Copter: never send unhealthy terrain status

Copter does not yet rely on the terrain data (it's for informational
purposes only) so we will temporarily disable the failure flags to the
GCS to avoid support calls

ArduCopter/GCS_Mavlink.pde

@@ -224,9 +224,10 @@ static NOINLINE void send_extended_status1(mavlink_channel_t chan)
     case AP_Terrain::TerrainStatusDisabled:
         break;
     case AP_Terrain::TerrainStatusUnhealthy:
-        control_sensors_present |= MAV_SYS_STATUS_TERRAIN;
-        control_sensors_enabled |= MAV_SYS_STATUS_TERRAIN;
-        break;
+        // To-Do: restore unhealthy terrain status reporting once terrain is used in copter
+        //control_sensors_present |= MAV_SYS_STATUS_TERRAIN;
+        //control_sensors_enabled |= MAV_SYS_STATUS_TERRAIN;
+        //break;
     case AP_Terrain::TerrainStatusOK:
         control_sensors_present |= MAV_SYS_STATUS_TERRAIN;
         control_sensors_enabled |= MAV_SYS_STATUS_TERRAIN;