testinfra : add system-config as required project
testinfra : add system-config as required project

Because this job is defined in system-config repo, when it runs there
it has system-config.  When we're trying to run it against upstream
testinfra we need to ensure we pull it in explicitly.

Change-Id: I2bbba366501f10744ffaf26d1acfa54d652afae3

openstack-infra/project-config,openstack-infra/project-config