JIRA: https://jira.spring.io/browse/INT-4382
There is a deadlock in the FMWH due to lock ordering.
Writes try to lock the handler monitor while holding the file lock.
The `Flusher` tries to lock the file lock while holding th handler monitor.
- Change the `Flusher`, `stop` and `flushIfNeeded` methods to not call close
on the file state while holding the handler monitor.
__cherry pick to 4.3.x__ (fix <> for Java 6)
Polishing - PR Comments
* Optimize `flushIfNeeded(FlushPredicate)` to delegate only to the
`flushIfNeeded(MessageFlushPredicate, Message<?>)`
55d92edd4e