tests: add tests for handling of corrupt extents

Add some regression tests to examine how e2fsck deals with (a) extent
blocks with only a bad checksum; (b) extent blocks with a bad magic
number; and (c) extent entries with corruption.

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