lockd: Split nlm_release_call()

The nlm_release_call() function is invoked from both the server and
the client side.  We're about to introduce a distinct server- and
client-side nlm_release_host(), so nlm_release_call() must first be
split into a client-side and a server-side version.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>