smb: test closing failed dial connections

Followup to:

74f9f182aa smb: fix TCP connection leak when connection setup fails - #9678

(cherry picked from commit 23f1dbfe50)
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f