BUG/MINOR: resolvers: Consider server to have no IP on DNS resolution error

BUG/MINOR: resolvers: Consider server to have no IP on DNS resolution error

When an error is received for a DNS resolution, for instance a NXDOMAIN
error, the server must be considered to have no address when its status is
updated, not the opposite.

Concretly, because this parameter is not used on error path in
snr_update_srv_status(), there is no impact.

This patch must be backported as far as 1.8.

(cherry picked from commit bd0227c1096ecc9e11da315c399b178b16ad7a9d)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>