Defend agains exceptions in application initialisation

Application initialisation code (as found in initialize function)
can raise an exception, which would break entire pipeline set-up.

This fix catches and logs the exception. The application is not
removed - it can continue to work on a best-effort basis.

TrivialFix

Change-Id: I5c2f00578ba5208ab7fed4441e4919cd3d71ae34

dragonflow/switch/drivers/ovs/datapath.py

@@ -112,8 +112,11 @@ class Datapath(object):
 
         self.write_datapath_allocation()
 
-        for app in self.apps.values():
-            app.initialize()
+        for name, app in self.apps.items():
+            try:
+                app.initialize()
+            except Exception:
+                LOG.exception('Failed to initialize %s (%s)', name, app)
 
         for edge in self._layout.edges:
             self._install_edge(edge)