xfs_db: enable blocktrash for checksummed filesystems

xfs_db: enable blocktrash for checksummed filesystems

Disable the write verifiers when we're trashing a block.  With this
in place, create a xfs fuzzer script that formats, populates, corrupts,
tries to use, repairs, and tries again to use a crash test xfs image.
Hopefully this will shake out some v5 filesystem bugs.

This allow trashing of log blocks and symlinks, and require the
caller to explicitly ask for trashing of log blocks and super
blocks.  Allowing log blocks by default skews the trashing heavily
in favor of (probably unused) log blocks, which doesn't help us with
fuzzing.  Furthermore, trashing the superblock results in a time
consuming sector by sector superblock hunt.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>