request-id needs to be stored in thread local store to allow
openstack.common.log use request-id.
tenant_name and user_name are added to the context so that
they can be logged by customizing the log format.
Also replaces 'cxt' with 'ctx' in test_neutron_context.py.
Previously both 'ctx' and 'cxt' are used mixed in one file.
Change-Id: Ib921585e648e92491c1366bc0ad26a6ae71e2fc9
Partial-Bug: #1239923