During the upgrade test we can trigger a re-render of the Vault secret due to
client restart before the allocrunner has marked the task as running, which
triggers the change mode on the template and restarts the task. This results in
a race where the alloc is still "pending" when we go to check it. We never
change the value of this secret in upgrade testing, so paper over this race
condition by setting a "noop" change mode.
