Pulp

This issue was caused by the introduction of the vars pulp_settings_file and pulp_config_dir to the pulp role (with default values), but it being used in other roles as well.

[The previous solution](https://github.com/pulp/ansible-pulp/pull/183) (now closed w/o merge) to this problem was to declare static dependencies of the other roles on the pulp role, but this means that if the roles are dynamically called, the pulp role will be re-run even more times.

I now believe the better solution is to add the 2 variables to the "defaults" of all roles that use it. So that it is a loosely coupled variable/role. We do this already for some other variables (pulp_user & pulp_install_dir).