Fixes the swift loopback device creation for test setup.

If CONFIG_SWIFT_STORAGES stays blank, packstack should create one loopback
device for swift instead of two (/srv/node/swift_loopback and
/srv/node/swiftloopback).

Change-Id: Id961c4a284abf5b6a2a8d2fccdc0ea7ff498d4a0
Fixes: rhbz#1141125
Signed-off-by: Gael Chamoulaud <gchamoul@redhat.com>
Merge "Fixes the swift loopback device creation for test setup."