Debian 10 support

[JvGinkel]

Hi Guys, I have a bit of an issue with the merged debian 10 support https://github.com/voxpupuli/puppet-mongodb/pull/619/files

With defining a version to 4.4.8 https://github.com/voxpupuli/puppet-mongodb/blob/master/manifests/globals.pp#L20 puppet will make sure that 4.4.8 is being installed.

All of our servers are being patched every month with a apt upgrade and this process will upgrade the mongo packages to the latest version. But in the next puppet run puppet it will downgrade again to 4.4.8.

We can resolve this by adding a apt::pin so that the mongo packages are pinned to this version.

The other issue I have is that we are now managing patch versions from puppet. With the $version to undef and the mongodb::repo::version: '4.4' we make sure we have a version 4.4.X installed and our normal patching would do the patch upgrades. (so for example from 4.4.0 to 4.4.1)

So before making pull-request I'm interested in your opinions about this. I think we need to apt::pin packages when we provide a specific version but I would also like to keep the version to undef and we set a repo version to for example 4.4 so our normal patch process can do the patch-upgrades.