don't parse subdirs in host/group_vars

as those are not supported in
core vars_plugins/group_vars.py
but might be used by other vars_plugins
Merge pull request #2899 from sergevanginderachter/host-group-vars-no-subdirs

don't parse subdirs in host/group_vars
Fix listification inside of with_items so it runs more intelligently.
Merge branch 'devel' into local