manage a coherent symlink when all the packages build
manage a coherent symlink when all the packages build

This allows to be sure the packages are coherent with all
the upstream git repositories with no outdated packages.

Handle the case where packages were never built.

Change-Id: Ic6529552e60e365d42820923dd03888732810630

openstack-packages/DLRN,openstack-packages/DLRN,openstack-packages/delorean,openstack-packages/delorean