Copter: fence breach causes disarm if landed

Previously it would only disarm if the throttle was also at zero.
Pair programmed with Tridge

ArduCopter/fence.pde

@@ -28,9 +28,9 @@ void fence_check()
         // if the user wants some kind of response and motors are armed
         if(fence.get_action() != AC_FENCE_ACTION_REPORT_ONLY ) {
 
-            // disarm immediately if we think we are on the ground
+            // disarm immediately if we think we are on the ground or in a manual flight mode with zero throttle
             // don't disarm if the high-altitude fence has been broken because it's likely the user has pulled their throttle to zero to bring it down
-            if(ap.land_complete || manual_flight_mode(control_mode) && ap.throttle_zero && !failsafe.radio && ((fence.get_breaches() & AC_FENCE_TYPE_ALT_MAX)== 0)){
+            if (ap.land_complete || (manual_flight_mode(control_mode) && ap.throttle_zero && !failsafe.radio && ((fence.get_breaches() & AC_FENCE_TYPE_ALT_MAX)== 0))){
                 init_disarm_motors();
             }else{
                 // if we are within 100m of the fence, RTL