Don't use default interface name for ironic underlay template

- rename BAREMETAL_ADMIN_IFACE to IRONIC_LAB_PXE_IFACE in the
ironic underlay template to avoid intersections

Change-Id: I011b0a3030ee5b49f78a618542c4f0e1bf0f663a
diff --git a/tcp_tests/templates/ironic_standalone/underlay.yaml b/tcp_tests/templates/ironic_standalone/underlay.yaml
index 664665c..0753174 100644
--- a/tcp_tests/templates/ironic_standalone/underlay.yaml
+++ b/tcp_tests/templates/ironic_standalone/underlay.yaml
@@ -67,7 +67,7 @@
             address_pool: provisioning-pool01
             dhcp: false
             parent_iface:
-              phys_dev: !os_env BAREMETAL_ADMIN_IFACE, enp8s0f1
+              phys_dev: !os_env IRONIC_LAB_PXE_IFACE
 
 
         nodes: