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/core/process.py b/src/osmo_gsm_tester/core/process.py
index 33ae69a..8954674 100644
--- a/src/osmo_gsm_tester/core/process.py
+++ b/src/osmo_gsm_tester/core/process.py
@@ -347,7 +347,7 @@
         return self.result is not None
 
     def wait(self, timeout=300):
-        MainLoop.wait(self, self.terminated, timeout=timeout)
+        MainLoop.wait(self.terminated, timeout=timeout)
 
     def stdin_write(self, cmd):
         '''