A Gearman client can set a client id which is then used on the server
side to identify the connection. Lack of a client_id makes it harder to
follow the flow when looking at logs:
gear.Connection.b'unknown' INFO Connected to 127.0.0.1 port 4730
gear.Server Accepted connection
<gear.ServerConnection ... name: None ...>
In RPCClient, introduce a client_id argument which is passed to
Update callers to set a meaningful client_id.