ubik: cleanup DB lock usage in SDISK_SendFile

ubik: cleanup DB lock usage in SDISK_SendFile

Some failure paths can return from SDISK_SendFile with the
database lock still held.  Other failure paths will cause
setlabel to be called without holding the lock.

Rework the failure paths so we always release the DB lock before
returning, and always hold it when calling setlabel.

Change-Id: I4cf98ecc9874110273e2cb4f94c37bdb9b43f0a2
Reviewed-on: http://gerrit.openafs.org/4151
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>