PYTHON-2634 Skip arbiter tests when no server is running (#611)

(cherry picked from commit 6412fed)

Author: ShaneHarvey

test/test_client.py

@@ -2036,6 +2036,7 @@ def timeout_task():
 
 class TestClientPool(MockClientTest):
 
+    @client_context.require_connection
     def test_rs_client_does_not_maintain_pool_to_arbiters(self):
         listener = CMAPListener()
         c = MockClient(
@@ -2065,6 +2066,7 @@ def test_rs_client_does_not_maintain_pool_to_arbiters(self):
         arbiter = c._topology.get_server_by_address(('d', 4))
         self.assertFalse(arbiter.pool.sockets)
 
+    @client_context.require_connection
     def test_direct_client_maintains_pool_to_arbiter(self):
         listener = CMAPListener()
         c = MockClient(