[Test]: FIX dns_cache fix expired_in.
[Test]: FIX dns_cache fix expired_in.

ngx_now is imported by resty, so the expired_in is the current unixtime.
This validate that cache values are correct.

Signed-off-by: Eloy Coto <2a8acc28452926ceac4d9db555411743254cf5f9@gmail.com>

3scale/apicast,3scale/docker-gateway,3scale/docker-gateway,3scale/apicast,3scale/apicast,3scale/apicast