sensors: check other gyros on timeout

@bkueng reviewed this and found that it is dangerous to continue on
timeout because we don't update other gyro sensors in the timeout case.

src/modules/sensors/sensors.cpp

 /****************************************************************************
  *
- *   Copyright (c) 2012-2017 PX4 Development Team. All rights reserved.
+ *   Copyright (c) 2012-2018 PX4 Development Team. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -630,12 +630,8 @@ Sensors::run()
 		 * if a gyro fails) */
 		int pret = px4_poll(&poll_fds, 1, 50);
 
-		/* if pret == 0 it timed out - periodic check for should_exit(), etc. */
-		if (pret == 0) {
-			continue;
-		}
-
-
+		/* If pret == 0 it timed out but we should still do all checks and potentially copy
+		 * other gyros. */
 
 		/* this is undesirable but not much we can do - might want to flag unhappy status */
 		if (pret < 0) {