[Service-ui] Not clear that backing up all buckets is done by specifying no bucket

When creating a plan to backup with no buckets selected, it is unclear what the backup task is going to backup. Turns out it does backup any and all buckets that are on/added to the cluster but this is not clear from the UI. 

 

 
No bucket selected above but all buckets being backed-up.

Perhaps the repository should have a list of the buckets instead of '-' ? Or just 'All buckets/data'.