locks.c: add the fl_owner to nlm_compare_locks

Add the fl_owner to NLM compare locks. Since two different client can
present the same pid to the server it is not enough to distinguish locks
from different clients. The fl_owner field is a pointer to the struct
nlm_host which is unique for each client.

Signed-off-by: Marc Eshel <eshel@almaden.ibm.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>