Fixing a client socket shutdown bug when unconnected

This change fixes a minor bug with the client shutdown routine,
where an error would get thrown when attempting to call shutdown
on an unconnected socket. This error is now caught and suppressed,
since the client is already shutting down. A new client unit test
is included to cover this change.

kmip/services/kmip_client.py

@@ -246,8 +246,13 @@ class KMIPProxy(KMIP):
     def close(self):
         # Shutdown and close the socket.
         if self.socket:
-            self.socket.shutdown(socket.SHUT_RDWR)
-            self.socket.close()
+            try:
+                self.socket.shutdown(socket.SHUT_RDWR)
+                self.socket.close()
+            except OSError:
+                # Can be thrown if the socket is not actually connected to
+                # anything. In this case, ignore the error.
+                pass
             self.socket = None
 
     def create(self, object_type, template_attribute, credential=None):

kmip/tests/unit/services/test_kmip_client.py

@@ -97,6 +97,50 @@ class TestKMIPClient(TestCase):
     def tearDown(self):
         super(TestKMIPClient, self).tearDown()
 
+    def test_close(self):
+        """
+        Test that calling close on the client works as expected.
+        """
+        c = KMIPProxy(
+            host="IP_ADDR_1, IP_ADDR_2",
+            port=9090,
+            ca_certs=None
+        )
+        c.socket = mock.MagicMock()
+        c_socket = c.socket
+
+        c.socket.shutdown.assert_not_called()
+        c.socket.close.assert_not_called()
+
+        c.close()
+
+        self.assertEqual(None, c.socket)
+        c_socket.shutdown.assert_called_once_with(socket.SHUT_RDWR)
+        c_socket.close.assert_called_once()
+
+    def test_close_with_shutdown_error(self):
+        """
+        Test that calling close on an unconnected client does not trigger an
+        exception.
+        """
+        c = KMIPProxy(
+            host="IP_ADDR_1, IP_ADDR_2",
+            port=9090,
+            ca_certs=None
+        )
+        c.socket = mock.MagicMock()
+        c_socket = c.socket
+        c.socket.shutdown.side_effect = OSError
+
+        c.socket.shutdown.assert_not_called()
+        c.socket.close.assert_not_called()
+
+        c.close()
+
+        self.assertEqual(None, c.socket)
+        c_socket.shutdown.assert_called_once_with(socket.SHUT_RDWR)
+        c_socket.close.assert_not_called()
+
     # TODO (peter-hamilton) Modify for credential type and/or add new test
     def test_build_credential(self):
         username = 'username'