Fix typo in role_substitutions variable.
Fix typo in role_substitutions variable.

Key in role_substitution variable has typo, which causes splitstack
deployments with composable roles to fail.

Change-Id: I7fb798fa97329f3cb80121184596153daf3f1a63

redhat-openstack/infrared,redhat-openstack/infrared,redhat-openstack/infrared