branch-update-repo: Fix branching for tiny image recipes

The repo tiny-image-recipes has several settings related to Apertis release
which should not be changed, as the tests run a well known Apertis release
an on top an lxc container from the release under testing.

Fix the branching script accordingly.

Signed-off-by: Walter Lozano <walter.lozano@collabora.com>

release-scripts/branch-update-repo

@@ -139,7 +139,8 @@ update-repo-tiny-images(){
     if [ -f .gitlab-ci.yml ] && ! grep -q -w ${NEXT_RELEASE} .gitlab-ci.yml
     then
         sed -i "s/release: .*/release: ${NEXT_RELEASE}/" .gitlab-ci.yml
-        sed -i "s/release_version: .*/release_version: ${NEXT_RELEASE}/" lavatests/*.yaml
+        # Use \b since there are several settings, which should remain unchanged
+        sed -i "s/\brelease_version: .*/release_version: ${NEXT_RELEASE}/" lavatests/*.yaml
         sed -i "s/test_branch: .*/test_branch: ${OSNAME}\/${NEXT_RELEASE}/" lavatests/*.yaml
         git commit -s -m "Build to ${NEXT_RELEASE}" -a
     fi