Make update.py work with oslo.config

As we move modules out of openstack.common into the oslo
namespace package, we need to prevent update.py from
breaking any import statements using them. Rather than
build a super complicated regex to only detect the
proper instances of "oslo" to replace in places like the
defaults for option settings, just do the simple translation
between oslo -> base and then go back and fix the modules
we know have been moved.

Change-Id: I9686b94b4c7df8542964b30ba15f0a91d2b3d722
Signed-off-by: Doug Hellmann <doug.hellmann@dreamhost.com>