This commit modifies some smoke tests with real-world usage examples
instead of providing things like 'foo' that the module user must
replace in order to conduct a smoke test or try out example functionality.
Prior to this commit, the source.pp test included an apt source
named foo which broke the apt-get update exec when applied on a
target system. This commit removes it in favor of the puppetlabs
apt source which is valid on all target platforms.
