CI: Complete parallel Coveralls uploads

[psafont]

When uploading more than one coverage result to coveralls, it needs to be told when all of them are done

[coveralls]

coverage: 44.887%. first build
when pulling f40a624 on psafont:endcover
into 6969a8a on xapi-project:master.

[edwintorok]

The DCO complains when I try to use this on another branch:

commit 1262d198d75c6dadbca5d0c5c4cd2db93d6d0a6f (HEAD -> feature/perf, edwintorok/feature/perf)
Author: Bernhard Kaindl <bernhard.kaindl@cloud.com>
Date:   Thu Jun 27 12:00:00 2024 +0200

    CI: Complete parallel Coveralls uploads: Finish when done

    Signed-off-by: Pau Ruiz Safont <pau.ruizsafont@cloud.com>

Commit sha: 1262d19, Author: Bernhard Kaindl, Committer: Edwin Török; Expected "Bernhard Kaindl bernhard.kaindl@cloud.com", but got "Pau Ruiz Safont pau.ruizsafont@cloud.com".

I don't know why it didn't complain on the original PR

[psafont]

Maybe because it was cherry-picked and so you appear as the committer.

[edwintorok]

Maybe because if I cherry-pick then I become the commiter, so now the author is nowhere in the git object anymore

[edwintorok]

There are some race conditions in the CI run apparently, it complains about a missing build: #5761 (comment)