loadbalancer/config: Parse resolv.conf for DNS

Control plane in HA setup doesn't currently work using Podman.
This is because the haproxy DNS server is hard-coded to use
127.0.0.1:53, which is not available on Podman.

To get the actual NS address, /etc/resolv.conf must be consulted.
So this patch adds parse-resolv-conf to the haproxy resolvers block,
which makes HA control plane work on Podman instantly.

This works for Docker as well as resolv.conf is populated too.

pkg/cluster/internal/loadbalancer/config.go

@@ -40,7 +40,7 @@ global
   maxconn 100000
 
 resolvers docker
-  nameserver dns 127.0.0.11:53
+  parse-resolv-conf
 
 defaults
   log global