util/agents/usb_hid_relay: return value from get_output()

Add missing return in get_output() to propagate value returned
by a device specific function.

Fixes: 7ab6240 ("util/agents/usb_hid_relay: fix concurrent access")
Signed-off-by: Łukasz Stelmach <[email protected]>

Author: Łukasz Stelmach

labgrid/util/agents/usb_hid_relay.py

@@ -100,7 +100,7 @@ def set_output(self, number, status):
 
     def get_output(self, number):
         with self._claimed():
-            self._get_output(number)
+            return self._get_output(number)
 
 
 _relays = {}