Update common openstack code from oslo-incubator

* Update to oslo-incubator commit b17b268a269c4989d76267db5c2d49d4c20bd51d.
* Update usage of 'deferred_version_string' to 'cached_version_string'
* Add context values 'user' and 'tenant' for context-logging
* Remove prefixes that resolve to '%prog' in --version CLI output

Change-Id: I24d9a24ad1a6e9379008ea719c9cbd22899111f9
Merge "Update common openstack code from oslo-incubator"