Added support to prompt for support case for RH Dropbox log collection

- Changes to prompt with JS pop up box for support case when file_log_depot type is "FileDepotFtpAnonymousRedhatDropbox".
- Changed logs_collect method to pass support_case in options that is being store in args column of miq_queue table.

https://bugzilla.redhat.com/show_bug.cgi?id=965889

@brandondunne @dclarizio please review/test.
@h-kataria Using the log_depot method these lines can be reduce to:
```ruby
log_depot.update_attributes(:support_case => options[:support_case].presence)
```