plugin: name by underlying system, not surfacing service

IPFW and PF are used for more than just firewall and shaper, e.g.
NAT, policy routing or shaping, and the plugin framework supports
registering multiple user-facing services per file.

src/etc/inc/plugins.inc.d/ipfw.inc

@@ -27,9 +27,10 @@
 */
 
 
-function shaper_services()
+function ipfw_services()
 {
     global $config;
+
     $services = array();
 
     if (!empty($config['OPNsense']['TrafficShaper']['rules']['rule'])) {

src/etc/inc/plugins.inc.d/pf.inc

@@ -26,7 +26,7 @@
     POSSIBILITY OF SUCH DAMAGE.
 */
 
-function firewall_services()
+function pf_services()
 {
     global $config;