[autotest] usb_facade_native: Resets USB controller at init

Resets USB controller at init so the USB devices can be re-enumerated.
This solves the problem where USB device is incorrectly detected when
previous USB test failed to remove it.

BUG=chromium:543667
TEST=run audio_AudioBasicUSBPlayback test and let it failed. run
audio_AudioBasicHDMI test and see USB is not detected.

Change-Id: I65158745d578234b09e64bc960c244fc35b9312d
Reviewed-on: https://chromium-review.googlesource.com/307020
Commit-Ready: Cheng-Yi Chiang <cychiang@chromium.org>
Tested-by: Cheng-Yi Chiang <cychiang@chromium.org>
Reviewed-by: Hsinyu Chao <hychao@chromium.org>
Reviewed-by: Kalin Stoyanov <kalin@chromium.org>
diff --git a/client/cros/multimedia/usb_facade_native.py b/client/cros/multimedia/usb_facade_native.py
index 41ac987..79bf155 100644
--- a/client/cros/multimedia/usb_facade_native.py
+++ b/client/cros/multimedia/usb_facade_native.py
@@ -41,6 +41,7 @@
 
         """
         self._drivers_manager = USBDeviceDriversManager()
+        self._reenumerate_usb_devices()
 
 
     def _reenumerate_usb_devices(self):