Staging build: don't use _GIT_TAG
Staging build: don't use _GIT_TAG

The _GIT_TAG has a prefix vYYYYMMDD, so is not a valid semver.

Instead we use our CI=1 approach to construct a reasonable semver tag.

justinsb/kops,robinpercy/kops,robinpercy/kops,justinsb/kops,robinpercy/kops,kubernetes/kops,robinpercy/kops,kubernetes/kops,justinsb/kops,kubernetes/kops