networkd: when filtering out duplicate domain names use DNS comparison

When we collect the domain names of the various links and other sources in one ordered set, make sure to use proper DNS
name comparison to filter out duplicates.

src/network/networkd-manager.c

@@ -29,6 +29,7 @@
 #include "bus-util.h"
 #include "conf-parser.h"
 #include "def.h"
+#include "dns-domain.h"
 #include "fd-util.h"
 #include "fileio.h"
 #include "libudev-private.h"
@@ -852,11 +853,11 @@ static int manager_save(Manager *m) {
         if (!ntp)
                 return -ENOMEM;
 
-        search_domains = ordered_set_new(&string_hash_ops);
+        search_domains = ordered_set_new(&dns_name_hash_ops);
         if (!search_domains)
                 return -ENOMEM;
 
-        route_domains = ordered_set_new(&string_hash_ops);
+        route_domains = ordered_set_new(&dns_name_hash_ops);
         if (!route_domains)
                 return -ENOMEM;