Move rootwrap code to openstack.common

Copies current nova-rootwrap code to openstack.common, so that it
can be reused by Cinder and Quantum.

Implements blueprint common-rootwrap.

Before it can be used in projects, update.py needs to grow the
capability to deploy files in bin/ and etc/, as well as replacing
a placeholder text by the destination project name in source files
and binary names.

In this proposed version, the placeholder text is "oslo".

Change-Id: I8655d5b3cccacd1cc2225aa539339fb478615422
Merge "Move rootwrap code to openstack.common"