ext4: Fix fs corruption when make_indexed_dir() fails

When make_indexed_dir() fails (e.g. because of ENOSPC) after it has
allocated block for index tree root, we did not properly mark all
changed buffers dirty.  This lead to only some of these buffers being
written out and thus effectively corrupting the directory.

Fix the issue by marking all changed data dirty even in the error
failure case.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>