Fix wrong commit status in web ui (#26121)

Before:

After:


There's a bug in the recent logic, `CalcCommitStatus` will always return
the first item of `statuses` or error status, because `state` is defined
with default value which should be `CommitStatusSuccess`

Then
``` golang
if status.State.NoBetterThan(state) {
```
this `if` will always return false unless `status.State =
CommitStatusError` which makes no sense.
So `lastStatus` will always be `nil` or error status.
Then we will always return the first item of `statuses` here or only
return error status, and this is why in the first picture the commit
status is `Success` but not `Failure`.

https://github.com/go-gitea/gitea/blob/af1ffbcd63569df8646b20c524378f25710f129e/models/git/commit_status.go#L204-L211

Co-authored-by: Giteabot <teabot@gitea.io>