BUG/MEDIUM: proxy: do not wake stopped proxies' tasks during soft_stop()

BUG/MEDIUM: proxy: do not wake stopped proxies' tasks during soft_stop()

When performing a soft stop, we used to wake up every proxy's task and
each of their table's task. The problem is that since we're able to stop
proxies and peers not bound to a specific process, we may end up calling
random junk by doing so of the proxy we're waking up is already stopped.
This causes a segfault to appear during soft reloads for old processes
not bound to a peers section if such a section exists in other processes.

Let's only consider proxies that are not stopped when doing this.

This fix must be backported to 1.5 which also has the same issue.