improve performance and memory usage for dns_anx

when fetching all zones the memory usage can exceede limits and also
cause timeouts.

with this change the zone will be searched via the longest to shortest
match using the get endpoint.

dnsapi/dns_anx.sh

@@ -127,8 +127,6 @@ _get_root() {
   i=1
   p=1
 
-  _anx_rest GET "zone.json"
-
   while true; do
     h=$(printf "%s" "$domain" | cut -d . -f $i-100)
     _debug h "$h"
@@ -137,6 +135,7 @@ _get_root() {
       return 1
     fi
 
+    _anx_rest GET "zone.json/${h}"
     if _contains "$response" "\"name\":\"$h\""; then
       _sub_domain=$(printf "%s" "$domain" | cut -d . -f 1-$p)
       _domain=$h