* These can still race when multiple ansible processes are created at
the same time.
* Reverse order of expanduser and expandvars in unfrakpath(). So that
tildes in environment variables will be handled.
Required some rewiring in inventory code to make sure we're using
the DataLoader class for some data file operations, which makes mocking
them much easier.
Also identified two corner cases not currently handled by the code, related
to inventory variable sources and which one "wins". Also noticed we weren't
properly merging variables from multiple group/host_var file locations
(inventory directory vs. playbook directory locations) so fixed as well.
