afs: Retry unlock after afs_StoreAllSegments

afs: Retry unlock after afs_StoreAllSegments

HandleFlock calls afs_StoreAllSegments when unlocking an exclusive
flock lock. This can drop the write lock on avc, so we must
effectively retry the entire lock operation again, since the world may
have changed while we were waiting to reacquire the lock on avc. So,
retry once all of the lock checks up to that point, to ensure that a
lock on the file actually still exists.

FIXES 125446

Reviewed-on: http://gerrit.openafs.org/4393
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit 601fcf1d7f7c88cfc0ffd877c5458340b3e59098)

Change-Id: Ibd215d586485d8f18f77665f5f85e6bee579e35e
Reviewed-on: http://gerrit.openafs.org/5766
Reviewed-by: Derrick Brashear <shadow@dementix.org>
Tested-by: Derrick Brashear <shadow@dementix.org>