tests: add regression tests for MMP blocks with bad checksums

Add regression tests to examine how e2fsck deals with MMP blocks with
(a) a bad magic number; and (b) an incorrect checksum.

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