t/test.sh: fix occasional atime-related failure in metadata tests.
t/test.sh: fix occasional atime-related failure in metadata tests.

The 'stat' command prints files' atimes, which can be modified just by
looking at them.  There's no point comparing that, since it can change from
one run to the next for legitimate reasons.

Signed-off-by: Avery Pennarun <e03ccfb89d416c4697ad6970ce86a92c1c28a78e@gmail.com>

mhoeher/bup,ToxicFrog/bup,mhoeher/bup,gevaerts/bup,ToxicFrog/bup,tjanez/bup,pombredanne/bup,mhoeher/bup,mhoeher/bup,mhoeher/bup,ToxicFrog/bup,ToxicFrog/bup,pombredanne/bup,gevaerts/bup,pombredanne/bup,jbaber/bup,jbaber/bup,gevaerts/bup,pombredanne/bup,tjanez/bup,jbaber/bup,gevaerts/bup,tjanez/bup,jbaber/bup,tjanez/bup,pombredanne/bup,tjanez/bup,gevaerts/bup,apenwarr/bup,ToxicFrog/bup,apenwarr/bup,jbaber/bup,pombredanne/bup,mhoeher/bup,apenwarr/bup,tjanez/bup,apenwarr/bup,jbaber/bup