test: v4l2_videodevice: dequeue_watchdog: Check return value of streamOn

If the streamOn() call fails, there is no way the test will then
succeed. Catch it and return a failure.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Tested-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

test/v4l2_videodevice/dequeue_watchdog.cpp

@@ -50,7 +50,11 @@ protected:
 			}
 		}
 
-		capture_->streamOn();
+		ret = capture_->streamOn();
+		if (ret < 0) {
+			std::cout << "Failed to start streaming" << std::endl;
+			return TestFail;
+		}
 
 		timeout.start(5s);
 		while (timeout.isRunning()) {