Fix leak in send_iterate_fs

Fix a leak when generating a replication stream of a cloned dataset.

Reviewed-by: Matt Ahrens <mahrens@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Signed-off-by: Tim Crawford <tcrawford@datto.com>
Closes #6034

lib/libzfs/libzfs_sendrecv.c

@@ -870,6 +870,8 @@ send_iterate_fs(zfs_handle_t *zhp, void *arg)
 		}
 		VERIFY(0 == nvlist_add_uint64(nvfs, "origin",
 		    origin->zfs_dmustats.dds_guid));
+
+		zfs_close(origin);
 	}
 
 	/* iterate over props */