CHEF-3975: Added nested key test case

http://tickets.opscode.com/browse/CHEF-3975

Given a databag:

    { "id": "priestjim",
      "ssh": { "private": "....", "public": "..." }

then these should work:

    search(:users, 'ssh_private:*') or
    knife search users 'ssh_private:*'

However, the way open-source chef-server indexes databags, the original
gets index under the "raw_data" key. So these work instead:

    search(:users, 'raw_data_ssh_private:*') or
    knife search users 'raw_data_ssh_private:*'

These pedant tests recreates this bug. It tests that searching on
'ssh_private:*' works and searching on 'raw_data_ssh_private:*' does NOT
work.