proxyauth: make auth error handler return 401 for docker client

src/nginxconfig.ejs

@@ -258,6 +258,9 @@ server {
     }
 
     location @proxy-auth-login {
+        if ($http_user_agent ~* "docker-client") {
+            return 401;
+        }
         return 302 /login?redirect=$request_uri;
     }