DAFS: Allow LEAVE_OFF for DELETED volumes

DAFS: Allow LEAVE_OFF for DELETED volumes

When a volume is VOL_STATE_DELETED, it effectively does not exist to
other programs over FSSYNC. So, do not prevent someone from issuing a
FSYNC_VOL_LEAVE_OFF for a VOL_STATE_DELETED volume.

Reviewed-on: http://gerrit.openafs.org/4119
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit ddf5ae4f746f2b5e522e10cfcacb6225499e7956)

Change-Id: I840930e144260036e2c96d83134a79dee3c9d083
Reviewed-on: http://gerrit.openafs.org/4165
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>