This addresses a specific case with multiple vars files
in a group_vars/${groupname}/ directory where one of those files
is empty, which returns None instead of an empty dict.
Also adds play information into the hostvars creation, to assure the
variable manager used there has access to vars and vars_files
Fixes#9501Fixes#8213Fixes#7844
* PluginLoader class will now be more selective about loading some
plugin classes, if a required base class is specified (used to avoid
loading v1 plugins that have changed significantly in their apis)
* Added ability for the connection info class to read values from a
given hosts variables, to support "magic" variables
* Added some more magic variables to the VariableManager output
* Fixed a bug in the ActionBase class, where the module configuration
code was not correctly handling unicode
Serge van Ginderachter
James Cammarata
Benno Joy
Toshio Kuratomi