ext4: Fix update of mtime and ctime on rename

The patch below makes ext4 update mtime and ctime of the directory
into which we move file even if the directory entry already exists.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>