cls: add semantics for cls locks to require renewal without expiring

cls: add semantics for cls locks to require renewal without expiring

Add ability to *require* renewal of an existing lock in addition
toexisting ability to *allow* renewal of an existing lock. The key
difference is that a MUST_RENEW will fail if the lock has expired
(where a MAY_RENEW) will succeed. This provides calling code with the
ability to verify that a lock is held continually and that it was
never lost/expired.

Signed-off-by: J. Eric Ivancich <ivancich@redhat.com>