e2fsck: use root dir for lost+found when really desperate

e2fsck: use root dir for lost+found when really desperate

If we're totally unable to allocate a lost+found directory, ask the
user if he would like to dump orphaned files in the root directory.
Hopefully this enables the user to delete enough files so that a
subsequent run of e2fsck will make more progress.  Better to cram lost
files in the rootdir than the current behavior, which is to fail at
linking them in, thereby leaving them as lost files.

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