connection, metadata: do namespace translation as late as possible

connection, metadata: do namespace translation as late as possible

We have to do the namespace translation just before a message is
installed into the receiver's task, so we actually know about the
currently used pid and user namespaces.

To achive this, store the byte offset pointer in the message in
kdbus_conn_queue_alloc(), and patch the values over from
kdbus_conn_msg_install().

Thanks to Djalal Harouni for pointing this out.