stop poller threads on shutdown: cosmetics

cosmetics after gerrit

Change-Id: I4d982f83e3fe5a8c8c821ac718e51b9a58de2a62

frappy/secnode.py

@@ -257,13 +257,13 @@ class SecNode:
     def shutdown_modules(self):
         """Call 'shutdownModule' for all modules."""
         # stop pollers
-        for name in self.modules:
-            self.modules[name].stopPollThread()
+        for mod in self.modules.values():
+            mod.stopPollThread()
             # do not yet join here, as we want to wait in parallel
         now = time.time()
-        deadline = now + 5
-        for name in self.modules:
-            self.modules[name].joinPollThread(now - deadline)
+        deadline = now + 0.5  # should be long enough for most read functions to finish
+        for mod in self.modules.values():
+            mod.joinPollThread(max(0, deadline - now))
             now = time.time()
         for name in self._getSortedModules():
             self.modules[name].shutdownModule()