Fix branch used for package and bootstrap tests

The CI is attempting to find a branch of apertis-image-recipes with the name found in $CI_MERGE_REQUEST_TARGET_BRANCH_NAME for package and bootstrap testing. In the general case this works, however when the CI is testing packages in the <version>-updates or (presumably) <version>-security branches, this results in the CI looking for a branch called apertis/<version>-updates in apertis-image-recipes, which fails.

Resolve this by assembling the branch name to use from $OSNAME and $APERTIS_RELEASE instead of using $CI_MERGE_REQUEST_TARGET_BRANCH_NAME.

Signed-off-by: Martyn Welch martyn.welch@collabora.com