vol-salvage: VOL_DONE deleted volumes

vol-salvage: VOL_DONE deleted volumes

When the salvager deletes a volume (because it is an invalid RO clone,
or because there is no data associated with the volume), we should
inform the fileserver that the volume is gone. Otherwise, the volume
in the fileserver can get put into an error state (in DAFS) when it
tries to attach the volume, preventing anything from creating or using
that volume.

Change-Id: Iae7763b752a2bab7a529dd327d034fdb9e18664a
Reviewed-on: http://gerrit.openafs.org/4118
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>