rx: Make CALL_RELE and CALL_HOLD lock refcnt mutex

rx: Make CALL_RELE and CALL_HOLD lock refcnt mutex

The reference count mutex must always be held when calling CALL_RELE
or CALL_HOLD. Instead of requiring that the caller obtain, and release
the mutex, do so within the HOLD and RELE macros, greatly simplifying
calling code. Provide CALL_RELE_R and CALL_HOLD_R as versions of these
macros which can be used by callers who already hold the reference
count mutex for other purposes.

Change-Id: Ie3e9df8b9d2a79476f1707bd65e588f43271c636
Reviewed-on: http://gerrit.openafs.org/6219
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>
Tested-by: Jeffrey Altman <jaltman@secure-endpoints.com>