Revert "[KNIFE-437] remove default region and make region required"
Revert "[KNIFE-437] remove default region and make region required"

This reverts commit 5d9b96449bcf0e279174b86eddaa9932629bc1bd.

tdooner/knife-rackspace,chef/knife-rackspace,vhl/knife-rackspace,rackspace/knife-rackspace,philoserf/knife-rackspace,chef/knife-rackspace,decklin/knife-rackspace,srirajan/knife-rackspace,martinb3/knife-rackspace