e2fsck: insert a missing dirent tail for checksums if possible

e2fsck: insert a missing dirent tail for checksums if possible

If e2fsck is writing a block of directory entries to disk, it should
adjust the dirents to add the dirent tail if one is missing.  It's not
a big deal if there's no space to do this since rehash (pass 3A) will
reconstruct directories for us.  However, we may as well avoid
unnecessary work.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>