Correct region name of service catalog for identity V2 API

Currently the code of service catalog construction has a defect which
caused operator configured region name could not be able to apply into
the response of service catalog in such identity V2 APIs, and
"RegionOne" were used in any case [0] instead.

[0]
https://github.com/softlayer/jumpgate/blob/master/jumpgate/identity/drivers/sl/tokens.py#L210

Signed-off-by: Zhi Yan Liu <zhiyanl@cn.ibm.com>