Add shutdownModule function

Add and call shutdownModule function, in order to allow modules to clean
up.
use shutdownModule instead of shutdown to avoid confusion with
severs/dispatchers shutdown and to make it consistent with initModule
etc.
Try to resolve module dependencies

Change-Id: I2a091bf74ecadc2395fcdf92c599f1c49eb120f5
Reviewed-on: https://forge.frm2.tum.de/review/c/secop/frappy/+/31339
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
Reviewed-by: Alexander Zaft <a.zaft@fz-juelich.de>

frappy_demo/cryo.py

@@ -354,7 +354,7 @@ class Cryostat(CryoBase):
             timestamp = t
             self.read_value()
 
-    def shutdown(self):
+    def shutdownModule(self):
         # should be called from server when the server is stopped
         self._stopflag = True
         if self._thread and self._thread.is_alive():