Updated chefspecs + provider bugfix (Fixes #519)

There were 3 bugs fixed in this commit (one of them was introduced by
me in my refactor):

1.  node attribute `admin_groups` was being checked instead of `groups`
    in `find_dsh_group_members()`
2.  the node attribute branch for the dsh group was being overwritten
    in `configure_pubkey()`
3.  the `$HOME/.dsh` and `$HOME/.dsh/group` directories were being created
    with root ownership (instead of `user_admin` attribute value)

removed `create_dsh_information()` because everything about it was wrong.

corrected the chefspec examples (including a stub) to expect different
values, which correspond with the newly-refactored code.