Cannot delete sessions that failed to create while trying to download images larger than the remaining capacity

### What Operating System(s) are you seeing this problem on?

Linux (x86-64)

### Backend.AI version

22.09

### Describe the bug

Temporarily created sessions remain in the preparing state if image download fails.If you try to force a termination of that session, it stops in terminating state and does not disappear.

I think an exception is needed to remove temporary sessions when image down fails.

### To Reproduce

1. Download images larger than the remaining capacity.
1. Force termination of the session in the preparing state in the session list.
### Expected Behavior

_No response_

### Anything else?

_No response_

JIRA Issue: BA-219

No source files or tests are named. Reproduce the failure by attempting to download an image larger than the remaining capacity, then force-terminate the temporary session while it is preparing; trace the temporary-session creation, image-download failure, and termination paths. Done means the failed temporary session is removed instead of remaining in preparing or terminating.

Written by the indexing model from the issue text.