MINOR: resolvers: Reset server IP on error in resolv_get_ip_from_response()

MINOR: resolvers: Reset server IP on error in resolv_get_ip_from_response()

If resolv_get_ip_from_response() returns an error (or an unexpected return
value), the server is set to RMAINT status. However, its address must also
be reset. Otherwise, it is still reported by the cli on "show servers state"
commands. This may be confusing. Note that it is a theorical patch because
this code path does not exist. Thus it is not tagged as a BUG.

This patch may be backported as far as 2.0.

(cherry picked from commit 07ecff589d5e67eacfacfe62bccd70ea825b8bc0)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit b142fb40a4ce7566ee2ca42fb6b164f9402bbdcd)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>