Upgrade vcsrepo from 0.1.2 to 1.2.0

This fixes the dummy warning we're seeing during Puppet runs:

    Warning: Found multiple default providers for vcsrepo...

https://github.com/puppetlabs/puppetlabs-vcsrepo/pull/209
Merge pull request #690 from alphagov/upgrade-vcsrepo-1-2-0

Upgrade vcsrepo from 0.1.2 to 1.2.0