Fix 9248: challenge creator should not automatically join their own challenge (#10383)

* fix(challenges): creator should not join challenge automatically

* change behavior on the client side as well

* update tests and fix membercount

* update tests

* fix tests

website/server/libs/challenges/index.js

@@ -82,12 +82,10 @@ export async function createChallenge (user, req, res) {
   addUserJoinChallengeNotification(user);
 
   let results = await Promise.all([challenge.save({
-    validateBeforeSave: false, // already validate
-  }), group.save()]);
+    validateBeforeSave: false, // already validated
+  }), group.save(), user.save()]);
   let savedChal = results[0];
 
-  await savedChal.syncToUser(user); // (it also saves the user)
-
   return {savedChal, group};
 }