Copy testr log artifacts independent of OS logs.

* modules/openstack_project/files/jenkins_job_builder/config/devstack-gate.yaml:
Copy testr log artifacts independent of the OpenStack logs. Do this to
put the testr artifacts in the root of the jobs log dir. This is
consistent with the other testr log artifacts.

Change-Id: I4b83c78d83efdd9da8f99c72e85097370dffddc3
Merge "Copy testr log artifacts independent of OS logs."