tools/check_patch.py: Make script to return failure on check errors

In order to have the checker script to be useful as an
automated test tool, make it return errors when *any*
of the checks return a proper exit code. This wasn't
done before because it took a long time to curate and
check full pylint results (even filtered) and fix
false negatives.

Now hopefully we'll catch more easily silly syntax
errors and py 2.4 non compliances in the autotest
tree.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
tools/check_patch.py: Print all passed msg on clean check

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>