check: support include/exclude of sub groups

check: support include/exclude of sub groups

Allow including and/or excluding tests by test dir and group.
-g and -x command line arguments can take the form of
<subdir>/<group>.

For example:

./check -n -g xfs/quick
./check -n -g stress -x xfs/stress
./check -n -g xfs/punch -x dangerous_fuzzers

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>