Use parameters in config file for trust test
Use parameters in config file for trust test

``create_ctx_from_trust`` creates a context using project_id
and user_id that are set to blazar configuration file, but
the test is fixed to use "admin", which can cause unpredictable
unit test error on developer's local environment.

This patch fixes the problem.

Change-Id: Ied2451d8821dc0ac3f59fe838efec01453839909
Closes-Bug: #1777399

openstack/blazar,openstack/blazar,ChameleonCloud/blazar,ChameleonCloud/blazar,stackforge/blazar,stackforge/blazar