Ensure package updates don't happen unexpectedly

Ensure package updates don't happen unexpectedly

I'm seeing this run yum update on deploy, even though hiera
tripleo::packages::enable_upgrade says false.

I assume these are needed because we're getting "false", but I'm
unclear if this is a recently introduced problem (I only noticed it
today as my image has outdated centos packages and it thus hung on
step2 of the deploy.

Change-Id: If09cdde9883f2674dbbc40944be5fe4445caa08e
Closes-Bug: #1652107