Drop event_loop global functions and import MainLoop

Take the chance to identify and drop modules importing event_loop but
not using it.

Change-Id: Ifa1940cd00138ebc72fbcfd45a0e28246f7a5ed9
diff --git a/src/osmo_gsm_tester/process.py b/src/osmo_gsm_tester/process.py
index 4c55fe9..8ae6a55 100644
--- a/src/osmo_gsm_tester/process.py
+++ b/src/osmo_gsm_tester/process.py
@@ -23,7 +23,8 @@
 import signal
 from datetime import datetime
 
-from . import log, event_loop
+from . import log
+from .event_loop import MainLoop
 from .util import Dir
 
 class Process(log.Origin):
@@ -204,7 +205,7 @@
         return self.result is not None
 
     def wait(self, timeout=300):
-        event_loop.wait(self, self.terminated, timeout=timeout)
+        MainLoop.wait(self, self.terminated, timeout=timeout)
 
 
 class RemoteProcess(Process):