Require os specific repo

Without specifying the osfamily option, it attempts to install the package before the repsitory.

		E: Unable to locate package virtualbox-4.2
		E: Couldn't find any package by regex 'virtualbox-4.2'
		
		Error: /Stage[main]/Virtualbox/Package[virtualbox-4.2]/ensure: change from purged to present failed: Execution of '/usr/bin/apt-get -q -y -o DPkg::Options::=--force-confold install virtualbox-4.2' returned 100: Reading package lists...
		Building dependency tree...
		Reading state information...
		E: Unable to locate package virtualbox-4.2
		E: Couldn't find any package by regex 'virtualbox-4.2'
		
		Notice: /Stage[main]/Virtualbox::Repo::Debian/Apt::Source[virtualbox]/Apt::Key[Add key: 98AB5139 from Apt::Source virtualbox]/Exec[01f81ffb7fa3d1f9648ada7fcfa5d72e0f0e7eac]/returns: executed successfully
		Notice: /Stage[main]/Virtualbox::Repo::Debian/Apt::Source[virtualbox]/Apt::Pin[virtualbox]/File[virtualbox.pref]/ensure: created
		Notice: /Stage[main]/Virtualbox::Repo::Debian/Apt::Source[virtualbox]/File[virtualbox.list]/ensure: created
		Notice: /Stage[main]/Apt::Update/Exec[apt_update]: Triggered 'refresh' from 1 events
		Notice: Finished catalog run in 11.11 seconds