[BUG] ensure that we correctly re-start old process in case of error

[BUG] ensure that we correctly re-start old process in case of error

When a new process fails to grab some ports, it sends a signal to
the old process in order to release them. Then it tries to bind
again. If it still fails (eg: one of the ports is bound to a
completely different process), it must send the continue signal
to the old process so that this one re-binds to the ports. This
is correctly done, but the newly bound ports are not released
first, which sometimes causes the old process to remain running
with no port bound. The fix simply consists in unbinding all
ports before sending the signal to the old process.