Sort and shuffle SRV record by priority and weight

On multiple occasions, SRV query answers were not properly sorted by
priority. Records with same priority weren't randomized and shuffled.
This caused FreeIPA to contact the same remote peer instead of
distributing the load across all available servers.

Two new helper functions now take care of SRV queries. sort_prio_weight()
sorts SRV and URI records. query_srv() combines SRV lookup with
sort_prio_weight().

Fixes: https://pagure.io/freeipa/issue/7475
Signed-off-by: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Rob Crittenden <rcritten@redhat.com>

ipalib/util.py

@@ -981,14 +981,13 @@ def detect_dns_zone_realm_type(api, domain):
 
     try:
         # The presence of this record is enough, return foreign in such case
-        result = resolver.query(ad_specific_record_name, rdatatype.SRV)
+        resolver.query(ad_specific_record_name, rdatatype.SRV)
+    except DNSException:
+        # If we could not detect type with certainty, return unknown
+        return 'unknown'
+    else:
         return 'foreign'
 
-    except DNSException:
-        pass
-
-    # If we could not detect type with certainity, return unknown
-    return 'unknown'
 
 def has_managed_topology(api):
     domainlevel = api.Command['domainlevel_get']().get('result', DOMAIN_LEVEL_0)