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.

Reviewed-on: http://gerrit.openafs.org/4151
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit ad63745f357e377c613881fa3470b85d4d36fe36)

Change-Id: I99cb359f108f604be75f19250fb697eb95b81947
Reviewed-on: http://gerrit.openafs.org/9418
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
Tested-by: BuildBot <buildbot@rampaginggeek.com>