MEDIUM: mworker/cli: close child and parent fds, setup listeners

MEDIUM: mworker/cli: close child and parent fds, setup listeners

Basically, this is the continuation of the previous commits. So, here after the
fork, worker process closes the "master" end of the copied CLI sockpair and
binds its end, ipc_fd[1], to the GLOBAL proxy listener.
mworker_cli_global_proxy_new_listener() guarantees that GLOBAL proxy will be
created, if it wasn't the case before.

Master process, at first, allocates the MASTER proxy, creates master CLI listener
(-S command line option) and reload sockpair and then closes the "worker" end of
the copied CLI sockpair and binds its end, ipc_fd[0], to the created MASTER proxy.

Usage of the new PROC_O_INIT state helps to reduce test conditions to find the
newly forked worker.