config_server_checks.js should assert if initial replSetConfig fails

The config_server_checks.js test runs

rst.nodes[0].adminCommand(

);

We expect this to cause a network exception due to the node removing itself, but if it does not we should check the result of the command and assert if it is not OK. Otherwise it will fail in

expectState(rst, ReplSetTest.State.REMOVED);

which makes it harder to see that the problem was that the initiate failed, not that the node didn't become REMOVED.