vol: clear ih_synced before dropping lock

vol: clear ih_synced before dropping lock

in ih_reallyclose() clear ihP->ih_synced before dropped
the IH_LOCK.  ih_reallyclose() is already committed to
performing the OS_SYNC() call.  Failing to clear the ih_synced
flag before dropping the lock permits another thread, the ih_sync_all()
thread for example, to also conclude that it must sync the
file.

Reviewed-on: http://gerrit.openafs.org/3696
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 9e689e96099dba5227e62ea2c6069062daaac85a)

Change-Id: I18baf1e1cd409a108845c2db2cb38144593016c8
Reviewed-on: http://gerrit.openafs.org/3845
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>