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

*** 386,405 ****
   * 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_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;
          struct knetconfig       ns_knc;          /* (c) */
          struct netbuf           ns_addr;         /* (c) */
          CLIENT                  *ns_handle;      /* (c) */
          CLIENT                  *ns_addr_handle; /* (c) */
  };
--- 386,405 ----
   * It's used because there exist a possibility of simultaneous
   * execution of NLM shutdown operation and host monitor/unmonitor
   * operations.
   *
   * struct nlm_nsm:
!  *  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 {
!         kmutex_t                ns_lock;
          struct knetconfig       ns_knc;          /* (c) */
          struct netbuf           ns_addr;         /* (c) */
          CLIENT                  *ns_handle;      /* (c) */
          CLIENT                  *ns_addr_handle; /* (c) */
  };