viced: Allow checkout of VOL_STATE_DELETED volumes
The fileserver allows nonexistent volumes to be checked out. Since
VOL_STATE_DELETED volumes conceptually do not exist, we should also
allow them to be checked out.
Change-Id: Ibc0f761569b339579acff03a3cbd9f795f783e0a
Reviewed-on: http://gerrit.openafs.org/2873 Reviewed-by: Tom Keiser <tkeiser@sinenomine.net> Reviewed-by: Derrick Brashear <shadow@dementia.org> Tested-by: Derrick Brashear <shadow@dementia.org>