e2fsck: Fix bug which can cause e2fsck -fD to corrupt non-indexed directories

e2fsck: Fix bug which can cause e2fsck -fD to corrupt non-indexed directories

E2fsprogs 1.41.10 introduced a regression (in commit b71e018) where
e2fsck -fD can corrupt non-indexed directories when are exists one or
more file names which alphabetically sort before ".".  This can happen
with ext2 filesystems or for small directories (take less than a
block) which contain filenames that begin with a space or some other
punctuation mark.

Fix this by making sure we never reorder the '.' or '..' entry in the
directory, since they must be first.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>