ihandle release locking simplification

ihandle release locking simplification

several callers drop locks so ih_release can be called unlocked,
then relock. simply allow a locked call (via _ih_release_r).

side effect: we had races before on refcnt check versus cleanup style.
this addresses it, but only removes lock contention.

Change-Id: Id2d132baa170894ba3ab0e1e8d0bcf9cf6c0c712
Reviewed-on: http://gerrit.openafs.org/4271
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>