generic: test reflink side effects

Test that ctime gets updated and suid is cleared when we reflink.
Ensure we can't reflink about RLIMIT_FSIZE.  Ensure that we can't
expose stale preallocation block data when reflinking above EOF.
Make sure dedupe actually catches a single different byte.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>