EventLoop: Fix log error "Origin parent loop" during wait()

Setting the log.ctx manually is not needed anymore and it's actually
harmful since all palces where it was used, a log.Origin already in path
was being passed, causing a origin loop.

Change-Id: I0511b9f7bc59e3c7f2269ff3155d0c95db58d063
diff --git a/src/osmo_gsm_tester/obj/powersupply.py b/src/osmo_gsm_tester/obj/powersupply.py
index bc7c0e3..7715a46 100644
--- a/src/osmo_gsm_tester/obj/powersupply.py
+++ b/src/osmo_gsm_tester/obj/powersupply.py
@@ -47,7 +47,7 @@
     def power_cycle(self, sleep=0):
         """Turns off the device, waits N.N seconds, then turn on the device."""
         self.power_set(False)
-        MainLoop.sleep(self, sleep)
+        MainLoop.sleep(sleep)
         self.power_set(True)
 
 def get_instance_by_type(pwsupply_type, pwsupply_opt):