Refactor signal handling in openvpn_getaddrinfo

Refactor signal handling in openvpn_getaddrinfo

Pass in sig_info struct to use register signal instead of
modifying signal_received.

No functional changes though some may be warranted.
Questions:
  - Why are we overwriting SIGUSR1 in this function?
  - Why the special interrupted syscall treatment for getaddrinfo?
    Its not a syscall, is it?

Signed-off-by: Selva Nair <selva.nair@gmail.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20230101215109.1521549-3-selva.nair@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg25872.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>