Fix gitea admin setup, Add healthcheck

Added healthcheck to gitea database contaier.

Fixed initial admin setup checks - uses correct in-container user and
fixed fail checks.

roles/gitea/templates/docker-stack.yml.j2

@@ -47,6 +47,12 @@ services:
 
   db:
     image: postgres:13
+    healthcheck:
+      test: ["CMD", "pg_isready", "-q", "-U", "{{ gitea_db_username }}"]
+      interval: 1m
+      timeout: 10s
+      retries: 3
+      start_period: 1m
     volumes:
       - db:/var/lib/postgresql/data
     networks: