remove check for disallowing clones of backup or ro volumes

remove check for disallowing clones of backup or ro volumes

removes the if-statement ensuring that the volume being cloned is
not a backup volume, nor a read-only volume. This allows clones
from any type of volume to a given volume. Parent volume meta-data
is maintained, only the cloneId value changes.

Change-Id: If8444fcabc9b9106db7db7df881ae07e8d287915
Reviewed-on: http://gerrit.openafs.org/5046
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>