Revert "Merge pull request #387 from travis-ci/ps-tags"

This reverts commit aed9d2ff3a1890d652cc48b1823038c69f5ca395, reversing
changes made to 8ea6ed4988e15fbb50412fe2ad1c83910f3a1ff9.

I've tested these changes on both travis-staging and travis-pro-staging,
but unfortunately they resulted in an issue on travis-pro-gatekeeper
production, which I couldn't reproduce anywhere else.