BUG/MEDIUM: cli: crash when trying to access a worker

BUG/MEDIUM: cli: crash when trying to access a worker

When using the CLI proxy of the master and trying to access a worker
with the @ prefix, the worker just crash.

The commit 7216032 ("MEDIUM: mworker: leave when the master die")
reintroduced the old code of the pipe, which was not trying to access
the pointers before. The owner of the FD was modified to a different
value, this is a problem since we call listener_accept() in most cases
now from the mworker_accept_wrapper() and it casts the owner variable to
get the listener.

This patch fix the issue by setting back the previous owner of the FD.