The test always failed on systems with no support for zlib
inflateValidate and on systems where the png_set_option setting was
disabled, however pngtest-all succeeded because the failure was ignored.
The latter is now fixed so the badadler.png check needs to use --xfail,
not --relaxed.
Signed-off-by: John Bowler <jbowler@acm.org>
144b348e07