network: implement RPC calls for virNetworkUpdate

network: implement RPC calls for virNetworkUpdate

This is very short, because almost everything is autogenerated. All
that's needed are:

* src/remote/remote_driver.c: add pointer to autogenerated
    remoteNetworkUpdate to the function table for the remote
    network driver.

* src/remote/remote_protocol.x: add the "args" struct and add one more
    item to the remote_procedure enum for this function.

* src/remote_protocol-struct: update to match remote_protocol.x