lockd: Make lockd use rpc_new_client() instead of rpc_create_client

When doing NLM_GRANTED requests, lockd may end up blocking if we use
rpc_create_client() due to the synchronous call to rpc_ping(). Instead, use
rpc_new_client().

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>