Removed the use of non-standard ohai plugin

We now have a helper method `#address_for` to return the
IP of a given interface. Switched out the ohai use
in favor of `#address_for`.  Also, updated berkshelf
to 2.x which handles dep resolution correctly.  I run
into problems getting berkshelf to lock to the new 0.3.0
openstack-common w/o updating berkshelf.

Change-Id: If5988dc5290ed8d5faa3950c1995f9943d9efe65