Rover: Fixing issue 302

Using the configured FS_THR_VALUE to check for failsafe instead of
just checking against 50 below throttle min.

APMrover2/test.cpp

@@ -171,7 +171,7 @@ int8_t Rover::test_failsafe(uint8_t argc, const Menu::arg *argv)
 			fail_test++;
 		}
 
-		if (g.fs_throttle_enabled && channel_throttle->get_failsafe()){
+        if(g.fs_throttle_enabled && (channel_throttle->radio_in < g.fs_throttle_value)) {
 			cliSerial->printf_P(PSTR("THROTTLE FAILSAFE ACTIVATED: %d, "), channel_throttle->radio_in);
             print_mode(cliSerial, readSwitch());
             cliSerial->println();