Use latest bazel
It seems 0.27 is now too old. This is what happens when I go on vacation
apparently.
Add in a hack to override the bazelversion. We'll remove this once
https://gerrit-review.googlesource.com/c/gerrit/+/237495 lands and
has been merged up.
Change-Id: Ib7a6d33ce8bf8498fd5cd09b25087dc09acb8df4