Currently when SwiftAPI(common/swift.py) is initialized, region_name
is not specified; with multi-region setup, ironic may pick wrong swift
endpoint.
This fix loads region_name from keystone_authtoken/region_name, and
pass the value to SwiftAPI
Closes-Bug: #1554933
Change-Id: I7295fc96c3b9ed50214576e80723d1d9db1a7e38