Adding events in parallel does not work correctly
Steps to reproduce
Steps to reproduce:
1. Go to stable.opencast.org
2. Throttle connection speed in your browser to Fast 3G
3. Add a new event (upload a file)
4. While the event added in step 3 is still uploading, start adding another event (add a title for that event in the Add Event Wizard)
5. Wait until the upload of the Event of step 3 is completed
The Add Event Wizard is resetted, i.e. the metadata that you have entered is lost
The completion of an ongoing upload should not affect the creation of a new one.
Workaround (if any):
Don't add (scheduled) events in parallel
We need to reset the state of the wizard right after leaving the submit method. If we wait for the potentially long running requests to complete, the user might meanwhile have opened the wizard again and resetting the state causes loss of the data the user has entered.