We absolutely need:
Exec['apt_update'] -> Package<||>
To have the right OpenStack packages installed on Ubuntu and Debian.
So rather than installing with a Package resource, let's use an exec so
we are sure 'apt-get update' is run before any Package puppet resource.
Change-Id: Ic99304d546d1153e3244c1191bbfc52c2118dd5f
f68fc29524