add RemoteLogHandler independent of MainLogger

installing a custom logger was not possible, since the RemoteLogHandler
was not installed.
Additionally, search for the RemoteLogHandler recursively upwards, since
not all loggers copy their Hanlders to their children.

Change-Id: If3e19966d9289cacd926648582e9718b7eab279c
Reviewed-on: https://forge.frm2.tum.de/review/c/secop/frappy/+/34288
Reviewed-by: Alexander Zaft <a.zaft@fz-juelich.de>
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>

test/test_server.py

@@ -37,6 +37,11 @@ class LoggerStub:
     def getChild(self, *args):
         return self
 
+
+    def addHandler(self, *args):
+        pass
+
+
     info = warning = exception = error = debug
     handlers = []