autotest-firewalld-add-service: exit with status 1 when missing args

Don't exit with success help missing an argument.

Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>
autotest-firewalld-add-service: convert methods to static

The new PyCharm 3.0 will now suggest conversion to staticmethod when
a method doesn't use self, so I decided to try it out.

Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>