Expose private_floating_network_interface to stack outputs

The infromation will be used by automation to set correct interface for floating
network.

Related-Prod: PRODX-4286
Change-Id: I4d3df318f1d58b27a647629292d25b50b410ff4b
diff --git a/de/heat-templates/env/bmt410-mstr3-wrkr3-cmp0-gtw0-osd3.yaml b/de/heat-templates/env/bmt410-mstr3-wrkr3-cmp0-gtw0-osd3.yaml
index 623a26a..0475c50 100644
--- a/de/heat-templates/env/bmt410-mstr3-wrkr3-cmp0-gtw0-osd3.yaml
+++ b/de/heat-templates/env/bmt410-mstr3-wrkr3-cmp0-gtw0-osd3.yaml
@@ -33,6 +33,7 @@
   private_floating_network_ipam_pool_start: '172.16.51.31'
   private_floating_network_ipam_pool_end: '172.16.51.62'
   private_floating_network_gateway: '172.16.51.1'
+  private_floating_network_interface: 'os-floating'
   metallb_address_pools: [ '172.16.51.130-172.16.51.250' ]
   private_floating_interface: 'os-floating'
   storage_frontend_interface: 'ceph-control'