Currently we validate database_connection in 2 layers, each puppet
modules and puppet-oslo, however this makes it difficult to maintain
validation pattern because we always need to fix both.
This patch removes the validation from each puppet modules so that
we need to maitain only one place, puppet-oslo to update validation
logic.
Change-Id: I98808ac7e01709c0bf7e9d08a629255e080ccfa4