logread should not panic on an EOF, instead exiting gracefully

[deitch]

- What I did

logread (in pkg/memlogd) has an option to -f and follow. If not, then it reads until the end of the stream and exits.

Except it does not exit, it panic(), even if it is getting an EOF.

This changes it to exit sanely if it receives an EOF

- How I did it

Changed lines in pkg/memlogd/cmd/logread/main.go

- How to verify it

CI, and I did some manual testing. Beforehand, I got:

panic: EOF

goroutine 1 [running]:
main.main()
        /go/src/memlogd/cmd/logread/main.go:69 +0x426

After, it just exits cleanly

- Description for the changelog

Exit cleanly for logread when EOF