Correct reraising of exception

When an exception was caught and rethrown, it should call 'raise'
without any arguments because it shows the place where an exception
occured initially instead of place where the exception re-raised.

Change-Id: I57a1cb70ee7b7d839ccb86ae025b5161bd93a014

designate/backend/agent_backend/impl_djbdns.py

@@ -79,8 +79,8 @@ def filter_exceptions(fn):
     def wrapper(*a, **kw):
         try:
             return fn(*a, **kw)
-        except exceptions.Backend as e:
-            raise e
+        except exceptions.Backend:
+            raise
         except Exception as e:
             LOG.error(_LE("Unhandled exception %s"), str(e), exc_info=True)
             raise exceptions.Backend(str(e))

designate/backend/agent_backend/impl_knot2.py

@@ -141,7 +141,7 @@ class Knot2Backend(base.AgentBackend):
             except Exception as e:
                 self._execute_knotc('conf-abort')
                 LOG.info(_LI("Zone change aborted: %r"), e)
-                raise e
+                raise
             else:
                 self._execute_knotc('conf-commit')
 

designate/backend/impl_dynect.py

@@ -372,7 +372,7 @@ class DynECTBackend(base.Backend):
                     client.put(url, data=data)
                     break
             else:
-                raise e
+                raise
 
         client.put(url, data={'activate': True})
         client.logout()