autotest-firewall-add-service: autopep8 and remove unused import

general code cleanups

Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>
autotest-firewalld-add-service: remove unused variable

Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>
autotest-firewalld-add-service: spelling fix thanks to codespell

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