e2fsck: check for encrypted directory entries with too-short file names

e2fsck: check for encrypted directory entries with too-short file names

If there are directory entries with file names which are less than 16
bytes, it turns out that passing less than the crypto block size to
the kernel's crypto layer will cause the kernel to crash.

However, since there never should be encrypted directory entries where
the file name is less than 16 bytes (the AES block size), change
e2fsck to offer to address this corruption by deleting the directory
entry.

(We need to checks for this condition into the kernel as well.)

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