reset listening state for each secondary server (#4810)

The listenCallback() function is called for each secondary
address that a server should listen on. However, each call sets
the listening state to true, so subsequent addresses fail with
FST_ERR_REOPENED_SERVER. This commit resets the state on each
call.

lib/server.js

@@ -127,6 +127,7 @@ function multipleBindings (mainServer, httpHandler, serverOpts, listenOptions, o
           cb: (_ignoreErr) => {
             binded++
 
+            /* istanbul ignore next: the else won't be taken unless listening fails */
             if (!_ignoreErr) {
               this[kServerBindings].push(secondaryServer)
             }
@@ -144,6 +145,7 @@ function multipleBindings (mainServer, httpHandler, serverOpts, listenOptions, o
         mainServer.on('unref', closeSecondary)
         mainServer.on('close', closeSecondary)
         mainServer.on('error', closeSecondary)
+        this[kState].listening = false
         listenCallback.call(this, secondaryServer, secondaryOpts)()
       }
     }