Guard against double shutdown in client

If we have already performed a shutdown we can prevent exploding when
writing to self.wake_write if we short circuit.

Change-Id: If5352a373d5fa61dd1ee661f4a37976b3447dd9d

gear/__init__.py

@@ -1105,11 +1105,15 @@ class BaseClientServer(object):
 
         The object may no longer be used after shutdown is called.
         """
-        self.log.debug("Beginning shutdown")
-        self._shutdown()
-        self.log.debug("Beginning cleanup")
-        self._cleanup()
-        self.log.debug("Finished shutdown")
+        if self.running:
+            self.log.debug("Beginning shutdown")
+            self._shutdown()
+            self.log.debug("Beginning cleanup")
+            self._cleanup()
+            self.log.debug("Finished shutdown")
+        else:
+            self.log.warning("Shutdown called when not currently running. "
+                             "Ignoring.")
 
     def _shutdown(self):
         # The first part of the shutdown process where all threads

gear/tests/test_gear.py

@@ -287,6 +287,11 @@ class TestClient(tests.BaseTestCase):
         acl.revokeGrant('manager')
         self.assertFalse(acl.canGrant('manager'))
 
+    def test_double_shutdown(self):
+        client = gear.Client()
+        client.shutdown()
+        client.shutdown()
+
 
 def load_tests(loader, in_tests, pattern):
     return testscenarios.load_tests_apply_scenarios(loader, in_tests, pattern)