test.sh: don't try non-quick fsck on damaged repositories.

test.sh: don't try non-quick fsck on damaged repositories.

It turns out that older versions of git (1.5.x or so) have a git-verify-pack
that goes into an endless loop when it hits certain kinds of corruption, and
our test would trigger it almost every time.  Using --quick avoids calling
git-verify-pack, so it won't exhibit the problem.

Unfortunately this means a slightly less thorough test of non-quick
bup-fsck, but it'll have to do.  Better than failing tests nonstop, anyway.

Reported by Eduardo Kienetz.