Add default metadata for public network

Add deafult value for all models
Metadata will be replace in deployment by steps
from shared-salt:
https://github.com/Mirantis/tcp-qa/blob/master/tcp_tests/templates/shared-salt.yaml#L431

Change-Id: I99f4daaa0aee28ca6eca3b9cae3cc380c749d58d
diff --git a/tcp_tests/templates/cookied-bm-mcp-dvr-vxlan/salt-context-lab03-environment.yaml b/tcp_tests/templates/cookied-bm-mcp-dvr-vxlan/salt-context-lab03-environment.yaml
index 720c275..f9ae84b 100644
--- a/tcp_tests/templates/cookied-bm-mcp-dvr-vxlan/salt-context-lab03-environment.yaml
+++ b/tcp_tests/templates/cookied-bm-mcp-dvr-vxlan/salt-context-lab03-environment.yaml
@@ -95,3 +95,10 @@
           role: bond0_ab_dvr_vxlan_ctl_mesh_external
           external_address: 172.17.42.5
           external_network_netmask: 255.255.255.192
+
+environment_metadata:
+    public_gateway: 172.17.16.1
+    public_cidr: 172.17.16.0/24
+    public_allocation_start: 172.17.16.201
+    public_allocation_end: 172.17.16.245
+    tempest_test_target: gtw01*