Add several EnvVars and a default region for Rackspace driver
Add several EnvVars and a default region for Rackspace driver

Signed-off-by: Tao Wang <7e7be65ebb8f801a58c89ee3c1a6a687290e952e@gmail.com>

londoncalling/machine,docker/machine,voutilad/machine,Herbis/machine,dgageot/machine,SvenDowideit/machine,ibuildthecloud/machine,Herbis/machine,exoscale/docker-machine,ibuildthecloud/machine,SvenDowideit/machine,dgageot/machine,voutilad/machine,dweomer/docker-machine,larsla/machine,larsla/machine,flavio/machine,flavio/machine,dweomer/docker-machine,docker/machine,exoscale/docker-machine,londoncalling/machine