Fix data race when updating account

[wallyqs]

Fixes race that would make the TestJetStreamJWTMove test fail sometimes:

=== FAIL: server TestJetStreamJWTMove/non-tiered/R1 (4.79s)
==================
WARNING: DATA RACE
Write at 0x00c0014631f8 by goroutine 22900:
 github.com/nats-io/nats-server/v2/server.(*Server).updateAccountClaimsWithRefresh()
     /go/server/accounts.go:3535 +0x53dc
 github.com/nats-io/nats-server/v2/server.(*Server).UpdateAccountClaims()
     /go/server/accounts.go:3074 +0x45
 github.com/nats-io/nats-server/v2/server.(*Server).updateAccountWithClaimJWT()
     /go/server/server.go:1937 +0x3e5
 github.com/nats-io/nats-server/v2/server.(*Server).updateAccount()
     /go/server/server.go:1910 +0x1f1
 github.com/nats-io/nats-server/v2/server.(*Server).lookupAccount()
     /go/server/server.go:1875 +0x176
 github.com/nats-io/nats-server/v2/server.(*Server).LookupAccount()
     /go/server/server.go:1895 +0x2e4
 github.com/nats-io/nats-server/v2/server.(*Server).getRequestInfo()
     /go/server/jetstream_api.go:936 +0x2b4
 github.com/nats-io/nats-server/v2/server.(*Server).jsStreamCreateRequest()
     /go/server/jetstream_api.go:1285 +0xca
 github.com/nats-io/nats-server/v2/server.(*Server).jsStreamCreateRequest-fm()
     <autogenerated>:1 +0xcc
 github.com/nats-io/nats-server/v2/server.(*Server).processJSAPIRoutedRequests()
     /go/server/jetstream_api.go:799 +0x60c
 github.com/nats-io/nats-server/v2/server.(*Server).processJSAPIRoutedRequests-fm()
     <autogenerated>:1 +0x39
 github.com/nats-io/nats-server/v2/server.(*Server).startGoRoutine.func1()
     /go/server/server.go:3604 +0x27d

Previous read at 0x00c0014631f8 by goroutine 22995:
 github.com/nats-io/nats-server/v2/server.(*Server).updateAccount()
     /go/server/server.go:1902 +0x6d
 github.com/nats-io/nats-server/v2/server.(*Server).lookupAccount()
     /go/server/server.go:1875 +0x176
 github.com/nats-io/nats-server/v2/server.(*Server).LookupAccount()
     /go/server/server.go:1895 +0x4e
 github.com/nats-io/nats-server/v2/server.(*Server).updateInterestForAccountOnGateway()
     /go/server/leafnode.go:2030 +0x3a
 github.com/nats-io/nats-server/v2/server.(*client).processGatewayRSub.func1()
     /go/server/gateway.go:1966 +0xc4
 runtime.deferreturn()
     /usr/local/go/src/runtime/panic.go:476 +0x32
 github.com/nats-io/nats-server/v2/server.(*client).parse()
     /go/server/parser.go:664 +0x40b7
 github.com/nats-io/nats-server/v2/server.(*client).readLoop()
     /go/server/client.go:1373 +0x1c98
 github.com/nats-io/nats-server/v2/server.(*Server).createGateway.func1()
     /go/server/gateway.go:858 +0x37
 github.com/nats-io/nats-server/v2/server.(*Server).startGoRoutine.func1()
     /go/server/server.go:3604 +0x27d

Goroutine 22900 (running) created at:
 github.com/nats-io/nats-server/v2/server.(*Server).startGoRoutine()
     /go/server/server.go:3600 +0x2f2
 github.com/nats-io/nats-server/v2/server.(*Server).setJetStreamExportSubs()
     /go/server/jetstream_api.go:820 +0x178
 github.com/nats-io/nats-server/v2/server.(*Server).enableJetStream()
     /go/server/jetstream.go:425 +0xcf1
 github.com/nats-io/nats-server/v2/server.(*Server).EnableJetStream()
     /go/server/jetstream.go:217 +0x6f7
 github.com/nats-io/nats-server/v2/server.(*Server).Start()
     /go/server/server.go:2218 +0x1924
 github.com/nats-io/nats-server/v2/server.RunServer()
     /go/server/server_test.go:95 +0x30e
 github.com/nats-io/nats-server/v2/server.RunServerWithConfig()
     /go/server/server_test.go:117 +0x44
 github.com/nats-io/nats-server/v2/server.createJetStreamSuperClusterWithTemplateAndModHook()
     /go/server/jetstream_helpers_test.go:449 +0x1331
 github.com/nats-io/nats-server/v2/server.TestJetStreamJWTMove.func1()
     /go/server/jetstream_jwt_test.go:303 +0x204
 github.com/nats-io/nats-server/v2/server.TestJetStreamJWTMove.func3.2()
     /go/server/jetstream_jwt_test.go:409 +0x50
 testing.tRunner()
     /usr/local/go/src/testing/testing.go:1576 +0x216
 testing.(*T).Run.func1()
     /usr/local/go/src/testing/testing.go:1629 +0x47

Goroutine 22995 (running) created at:
 github.com/nats-io/nats-server/v2/server.(*Server).startGoRoutine()
     /go/server/server.go:3600 +0x2f2
 github.com/nats-io/nats-server/v2/server.(*Server).createGateway()
     /go/server/gateway.go:858 +0xf04
 github.com/nats-io/nats-server/v2/server.(*Server).solicitGateway()
     /go/server/gateway.go:707 +0x12e7
 github.com/nats-io/nats-server/v2/server.(*Server).solicitGateways.func1()
     /go/server/gateway.go:643 +0x44
 github.com/nats-io/nats-server/v2/server.(*Server).startGoRoutine.func1()
     /go/server/server.go:3604 +0x27d
==================
   testing.go:1446: race detected during execution of test
       --- FAIL: TestJetStreamJWTMove/non-tiered/R1 (4.79s)

=== FAIL: server TestJetStreamJWTMove/non-tiered (11.03s)
   testing.go:1446: race detected during execution of test
   --- FAIL: TestJetStreamJWTMove/non-tiered (11.03s)

=== FAIL: server TestJetStreamJWTMove (23.30s)
   testing.go:1446: race detected during execution of test

[Jarema]

We use this approach a lot in code, and the only thing it does, is prevent race detection, not actual race, because we use the acc.updated value outside of the mutex.

[wallyqs]

good point, so instead could do the check under the lock

[Jarema]

exactly.

[neilalexander]

LGTM, please rebase before merge, thanks!