Add multi_tenancy and session timeout config parameters in
default.config.global.js
If multi_tenancy is disabled, then while sending to API
Server, do not send X_API_ROLE in headers.
If session.timeout is set, then the
minimum value among this timeout and keystone token expiry will be taken as
session timeout, in case of cloudstack/no-orch, minimum if default session
timeout and this session.timeout will be set as session timeout value.

Change-Id: Ia7ed7241b1f22574a793a894efb3f896c6c135f0