Add a step to ensure that all repositories being tagged have a
.gitreview file. This ensures that the release job can properly clone
the repo and then establish a gerrit remote to submit
patches. Typically the file is missing for repos that are not fully
set up, or for repos that have been retired.
Change-Id: I1d8afeff40b7b4143486439ab2ab28925fea356e
Signed-off-by: Doug Hellmann <doug@doughellmann.com>