Mark all ZPL and ioctl functions as PF_FSTRANS

Prevent deadlocks by disabling direct reclaim during all ZPL and ioctl
calls as well as the l2arc and adapt ARC threads.

This obviates the need for MUTEX_FSTRANS so its previous uses and
definition have been eliminated.

Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #3225

module/zfs/dbuf.c

@@ -331,7 +331,7 @@ retry:
 	    0, dbuf_cons, dbuf_dest, NULL, NULL, NULL, 0);
 
 	for (i = 0; i < DBUF_MUTEXES; i++)
-		mutex_init(&h->hash_mutexes[i], NULL, MUTEX_FSTRANS, NULL);
+		mutex_init(&h->hash_mutexes[i], NULL, MUTEX_DEFAULT, NULL);
 
 	dbuf_stats_init(h);
 }