volser: Avoid assert on ViceCreateRoot failure

volser: Avoid assert on ViceCreateRoot failure

If IH_CREATE fails in ViceCreateRoot, it may just be due to an on-disk
inconsistency. So, don't assert, but just return an error and detach
the volume.

Reviewed-on: http://gerrit.openafs.org/4444
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 399655e3df3bf30d7878dec70402fc0021cae752)

Change-Id: Icbc934bfe59f6468771f37e5721341dae49ba460
Reviewed-on: http://gerrit.openafs.org/6285
Tested-by: Derrick Brashear <shadow@dementix.org>
Reviewed-by: Derrick Brashear <shadow@dementix.org>