Adjust the client perms at the end of the OSC upgrade process

Without this chef client runs won't work and will return 403
OSC upgrade: knife exec to update node permissions

By using `knife exec` to script the update of the node permissions, we
now have a framework in place to address any future permissions issues
that arise as a result upgrades from OSC. This also addresses the
current issue that prevents `chef-client` runs from completing on an
upgraded Chef Server.
Merge pull request #469 from opscode/mm/fix-node-perms

Adjust the client perms at the end of the OSC upgrade process

* fixes 464