DAFS: Do not VDeregisterVolOp_r while exclusive

DAFS: Do not VDeregisterVolOp_r while exclusive

We should wait for a volume to transition out of an exclusive state
before calling VDeregisterVolOp_r on a volume, since some code may be
examining the vol op outside of VOL_LOCK in an exclusive state. We
should be doing this anyway before performing volume state checks,
since we may be trying to e.g. attach the volume at the same time.

Reviewed-on: http://gerrit.openafs.org/4287
Tested-by: Andrew Deason <adeason@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit d4ebebd0c3f89b65e93f0da6d53665271e6d2a61)

Change-Id: I55f07806a4e089577252ddb527a86142b10f797d
Reviewed-on: http://gerrit.openafs.org/4306
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>