The .tarball-version file should contain the *source version* uniquely
identifying the git commit, and not the Debian package name.
With https://gerrit.osmocom.org/#/c/osmo-ci/+/10343/ there is a correct
.tarball-version file in the .tar.xz of the nightly source packages.
Change-Id: I093c9c1943e5f09d8f91f94af438f697a93e7127
Related: OS#3449