MINOR: DNS client query type failover management

MINOR: DNS client query type failover management

In the first version of the DNS resolver, HAProxy sends an ANY query
type and in case of issue fails over to the type pointed by the
directive in 'resolve-prefer'.
This patch allows the following new failover management:
1. default query type is still ANY
2. if response is truncated or in error because ANY is not supported by
   the server, then a fail over to a new query type is performed. The
   new query type is the one pointed by the directive 'resolve-prefer'.
3. if no response or still some errors occurs, then a query type fail over
   is performed to the remaining IP address family.