Use zfs range locks in ztest

The zfs range lock interface no longer tightly depends on a
znode_t and therefore can be used in ztest.  This allows the
previous ztest specific implementation to be removed, and for
additional test coverage of the shared version.

Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Boris Protopopov <boris.protopopov@actifio.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #4023
Issue #4024

include/sys/zfs_rlock.h

@@ -30,11 +30,14 @@
 extern "C" {
 #endif
 
-#ifdef _KERNEL
-
 #include <sys/list.h>
 #include <sys/avl.h>
+
+#ifdef _KERNEL
 #include <sys/condvar.h>
+#else
+#include <sys/zfs_context.h>
+#endif
 
 typedef enum {
 	RL_READER,
@@ -106,7 +109,6 @@ zfs_rlock_destroy(zfs_rlock_t *zrl)
 	avl_destroy(&zrl->zr_avl);
 	mutex_destroy(&zrl->zr_mutex);
 }
-#endif /* _KERNEL */
 
 #ifdef	__cplusplus
 }