MEDIUM: mworker: seamless reload use the internal sockpairs

With the master worker, the seamless reload was still requiring an
external stats socket to the previous process, which is a pain to
configure.

This patch implements a way to use the internal socketpair between the
master and the workers to transfer the sockets during the reload.
This way, the master will always try to transfer the socket, even
without any configuration.

The master will still reload with the -x argument, followed by the
sockpair@ syntax. ( ex -x sockpair@4 ). Which use the FD of internal CLI
to the worker.
5 files changed