[Content editor][Back port]Canceling a draft document deletes the changes without notifying the user

Steps to reproduce:

1. Go to the Content perspective

2. Select a document

3. Edit the document

4. Change the title of the document

5. Keep draft

6. Edit draft of the document

7. Click Cancel

Expected result:

There is a modal dialog asking the user if she wants the changes discarded. Also, the tooltip of the Cancel button should be clear that it also deletes the draft changes, if you open a draft document.

Actual result:

The draft changes of the document were lost without the user awareness.