nixos/elasticsearch: fix postStart to allow non-localhost listenAddress

Before this fix, if the listenAddress is set to something else than 127.0.0.1,
the service fails to detect that Elasticsearch has properly started and stop.

(cherry picked from commit 40fb59cfc3)

nixos/modules/services/search/elasticsearch.nix

@@ -204,7 +204,7 @@ in
       postStart = ''
         # Make sure elasticsearch is up and running before dependents
         # are started
-        while ! ${pkgs.curl}/bin/curl -sS -f http://localhost:${toString cfg.port} 2>/dev/null; do
+        while ! ${pkgs.curl}/bin/curl -sS -f http://${cfg.listenAddress}:${toString cfg.port} 2>/dev/null; do
           sleep 1
         done
       '';