problem

Create Instance from Backup feature added in #10140 .
Backup can be deleted after starting the Create Instance from Backup process which fails after some time saying backup doesn't exist.

versions

ACS 4.21.0

The steps to reproduce the bug

1. Start "Create Instance from Backup"
2. Delete the Backup used
3. Create Instance from Backup fails with error.
   ...

What to do about it?

Backup deletion should either be disallowed or queued until Create Instance from Backup is finished.