qa: make the directory non-empty to force migration

rank 0 will not migrate the directory until it is non-empty. And creating a
file and promptly deleting is not reliable; the vstart_runner.py test will just
loop forever.

Signed-off-by: Patrick Donnelly <[email protected]>

Author: batrick

qa/tasks/cephfs/test_data_scan.py

@@ -722,10 +722,10 @@ def test_rebuild_inotable(self):
         mds0_id = active_mds_names[0]
         mds1_id = active_mds_names[1]
 
-        self.mount_a.run_shell(["mkdir", "dir1"])
+        self.mount_a.run_shell_payload("mkdir -p dir1/dir2")
         dir_ino = self.mount_a.path_to_ino("dir1")
         self.mount_a.setfattr("dir1", "ceph.dir.pin", "1")
-        # wait for subtree migration
+        self._wait_subtrees([('/dir1', 1)], rank=1)
 
         file_ino = 0;
         while True: