Set fixture paths for unit tests
Set fixture paths for unit tests

This change defines manifest_dir and module_path expicitly in unit
tests so that modules installed under fixtures directory is properly
loaded.

Closes-Bug: #1930403
Change-Id: I3bb2b082e33c2843abcb97b0ae28b04dc33ac1ec

openstack/puppet-ceph,openstack/puppet-ceph,stackforge/puppet-ceph