Merge remote-tracking branch 'upstream/master' into linux

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

Conflicts:
	src/drivers/rgbled/rgbled.cpp
	src/modules/commander/PreflightCheck.cpp
	src/modules/commander/airspeed_calibration.cpp
	src/modules/commander/calibration_routines.cpp
	src/modules/commander/gyro_calibration.cpp
	src/modules/commander/mag_calibration.cpp
	src/modules/mc_att_control/mc_att_control_main.cpp

src/modules/uavcan/uavcan_main.cpp

@@ -698,7 +698,9 @@ int uavcan_main(int argc, char *argv[])
 
 	if (!std::strcmp(argv[1], "start")) {
 		if (UavcanNode::instance()) {
-			errx(1, "already started");
+			// Already running, no error
+			warnx("already started");
+			::exit(0);
 		}
 
 		// Node ID