Rover: consider GPS unhealthy if it doesn't have GPS lock

APMrover2/GCS_Mavlink.pde

@@ -158,7 +158,7 @@ static NOINLINE void send_extended_status1(mavlink_channel_t chan, uint16_t pack
     if (g.compass_enabled && compass.healthy() && ahrs.use_compass()) {
         control_sensors_health |= MAV_SYS_STATUS_SENSOR_3D_MAG;
     }
-    if (g_gps != NULL && g_gps->status() > GPS::NO_GPS) {
+    if (g_gps != NULL && g_gps->status() >= GPS::GPS_OK_FIX_3D) {
         control_sensors_health |= MAV_SYS_STATUS_SENSOR_GPS;
     }
     if (!ins.healthy()) {