Do a general cleanup of lib/dns/rpz.c style:

 * Removed deprecated and unused functions
 * Unified dns_rpz_zone_t naming to rpz
 * Unified dns_rpz_zones_t naming to rpzs
 * Add and use rpz_attach() and rpz_attach_rpzs() functions
 * Shuffled variables to be more local (cppcheck cleanup)

(cherry picked from commit 840179a2)