This dispatch job determines which image build jobs ran in gate
for a particular change and then filters the resulting job list
so that we don't attempt to promote images that were not built.
To simplify things, it relies on string substitution to match
the build and promote jobs. Since we're doing that, lets simplify
the promote jobs themselves to rely on the same substitution.
Change-Id: I6548b1a25f8bf7c943ba1fbfd41b6f01dba9b726
James E. Blair
571f86b6d0