syncevo-http-server: removed obsolete and harmful gobject.MainLoop

Instantiating gobject.MainLoop had two negative side effects:
- shutdown after CTRL-C got stuck
- SIGCHLD after syncevo-dbus-server shutdown also caused a deadlock

Not sure why the "loop = gobject.MainLoop()" was in the code;
it doesn't seem to serve any purpose anymore.

test/syncevo-http-server.py

@@ -91,8 +91,6 @@ class Context:
         Context.checkServer()
         return None
 
-loop = gobject.MainLoop()
-
 class SyncMLSession:
     sessions = []