rpcapd: add reuseaddr so daemon can be restarted quicky

[bleader]

In some cases (lost link then killing daemon for example), the listen port may still be in use when restarting the daemon. Using SO_REUSEADDR flag before bind() could help with this issue.

Given this is handled by the sock_open() function, I made my patch adding a call to setsockopt() before the bind() in case of server socket. This will also be applied in case of active connection, which may be unecessary but shouldn't create any issue, as far as I can tell.

The way I did it is on my fork, I wasn't able to test it on windows, but that should work, so I'll do a pull-request to check if CI builds fine.