Move apt-get update exec to a seperate class to minimize the number of
apt-get updates invoked by configuration changes.
* remove apt_update exec resource in apt class.
* remove apt-get-${name} in defines.
* apt::source notify Exec['apt update'].
* Remove dependency to Exec['apt_update'].
* fix rspec-puppet tests.
Conflicts:
manifests/source.pp
This patch adds the appropriate spec tests to validate the changes
introduced by e5f2dfe. As a bonus it includes fixes to the manifests
that were discovered while writing the tests.
