Issue title: When setting group app permission, select box stays on screen
 Issue body: 1) Enable checkbox to enable an app for a list of groups and select group(s)
2) choose a different app
3) selected groups box should disappear

 Comments: 
 Comment 0: Works for me in 8.1.3
{'source': 'GithubIssues', 'repo_name_with_owner': 'owncloud/core', 'issue_id': 51615326, 'repo_stars': 7873.0}