Add Ohai 15.6 releae notes
Add Ohai 15.6 releae notes

Signed-off-by: Tim Smith <764ef62106582a09ed09dfa0b6bff7c05fd7d1e4@chef.io>

chef/ohai,chef/ohai,higanworks/ohai,mattray/ohai,higanworks/ohai,jaymzh/ohai,jaymzh/ohai,mattray/ohai