dns: Make use of resolve_address of a current resolver instead of the global one

For now, `resolve_address` for dnspython < 2.0.0 is actually
the instance method of the global DNSResolver object and is not
the instance method of the corresponding object from which it was
called. This can result in unexpected behavior.

Signed-off-by: Stanislav Levin <slev@altlinux.org>
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>

ipapython/dnsutil.py

@@ -111,7 +111,7 @@ class DNSResolver(dns.resolver.Resolver):
         :param ip_address: IPv4 or IPv6 address
         :type ip_address: str
         """
-        return resolve(
+        return self.resolve(
             dns.reversename.from_address(ip_address),
             rdtype=dns.rdatatype.PTR,
             *args,