Currently, a client connection could send an initial hello/ismaster request without the internalClient field, and then later on send a subsequent hello command with internalClient: 1 specified, and the server would start treating this connection as an internal client connection.

We should change this so that the server does not allow a connection to change the value of internalClient after it has already sent the initial hello/ismaster request.
We should also add testing of this behavior.