tools/check_patch.py: attempt to unify script

We currently have different `check_patch.py` scripts (and possibly
other utility scripts) in autotest and virt-test. This is an
attempt to unify the script among the two code bases.

After this unification, keeping the two in synch can just be a
matter of copying the file to the other repo or maybe applying
the patch stripping the directory names which also differ on the
two repos.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
tool/check_patch.py: corrective actions member not used

Signed-off-by: Cleber Rosa <crosa@redhat.com>