XXXXX convert NLM's single-count semaphore to a mutex

@@ -386,20 +386,20 @@
  * It's used because there exist a possibility of simultaneous
  * execution of NLM shutdown operation and host monitor/unmonitor
  * operations.
  *
  * struct nlm_nsm:
- *  ns_sem: a semaphore for serialization network operations to statd
+ *  ns_lock: a mutex for serialization network operations to statd
  *  ns_knc: a kneconfig describing transport that is used for communication
  *  ns_addr: an address of local statd we're talking to
  *  ns_handle: an RPC handle used for talking to local statd using the status
  *      monitor protocol (SM_PROG)
  *  ns_addr_handle: an RPC handle used for talking to local statd using the
  *      address registration protocol (NSM_ADDR_PROGRAM)
  */
 struct nlm_nsm {
-        ksema_t                 ns_sem;
+        kmutex_t                ns_lock;
         struct knetconfig       ns_knc;          /* (c) */
         struct netbuf           ns_addr;         /* (c) */
         CLIENT                  *ns_handle;      /* (c) */
         CLIENT                  *ns_addr_handle; /* (c) */
 };