net-dns/unbound: runscript rewritten

net-dns/unbound: runscript rewritten

- "need net" changed to "use net". If you need to bind service to a specific
  interface or address add 'rc_need="<interface>"' in /etc/conf.d/<unbound>.

- Use "/run" instead of "/var/run".

- Verify daemon is really up and running.

- It is now possible to pass any by start-stop-daemon supported arguments
  to start-stop-daemon.

- It is now possible to preserve unbound's cache. [Bug 632644]

Closes: https://bugs.gentoo.org/632644
Package-Manager: Portage-2.3.49, Repoman-2.3.10