roles/logserver: use unstable version of loki and prometheus

roles/logserver.nix

@@ -26,12 +26,14 @@ in
     };
 
     environment.systemPackages = with pkgsUnstable; [
-      loki
+      grafana-loki
       prometheus
     ];
 
     services.loki = {
       enable = true;
+      package = pkgsUnstable.grafana-loki;
+
       configuration = {
         auth_enabled = false;
 
@@ -114,6 +116,7 @@ in
     services.prometheus = {
       enable = true;
       enableReload = true;
+      package = pkgsUnstable.prometheus;
       checkConfig = "syntax-only";
       extraFlags = [ "--web.enable-remote-write-receiver" ];