deployment: wrap packages with ensure_packages()

On beta, the deployment-bastion.eqiad.wmflabs instance is a Jenkins
slave which has zuul source code installed.  We end up with duplicate
packages for python-git / python-gitdb.

In zuul module, the package definition are already wrapped with
ensure_packages(), do the same in deployment_server.

Also removed git-core from deployment, it is part of the standard
packages definition and has ensure => latest which would be a dupe of
ensure => present provided by ensure_packages()

Change-Id: I5f126dd66330cea2dfc381b29a68d429d2428759
Merge "deployment: wrap packages with ensure_packages()" into production