APM_Control: reduce roll compensation in pitch controller by cos(pitch)

This reduces the use of the pitch compensation when in a steep climb
or dive

Pair-Programmed-With: Paul Riseborough <p_riseborough@live.com.au>

libraries/APM_Control/AP_PitchController.cpp

@@ -218,7 +218,7 @@ float AP_PitchController::_get_coordination_rate_offset(float &aspeed, bool &inv
         // don't do turn coordination handling when at very high pitch angles
         rate_offset = 0;
     } else {
-        rate_offset = fabsf(ToDeg((GRAVITY_MSS / max(aspeed , float(aparm.airspeed_min))) * tanf(bank_angle) * sinf(bank_angle))) * _roll_ff;
+        rate_offset = cosf(_ahrs.pitch)*fabsf(ToDeg((GRAVITY_MSS / max(aspeed , float(aparm.airspeed_min))) * tanf(bank_angle) * sinf(bank_angle))) * _roll_ff;
     }
 	if (inverted) {
 		rate_offset = -rate_offset;