Allow to pass custom vsrx image

Related-Prod: PRODX-11488
Change-Id: I3884a8cd3cd4129d7e74a5d425fffc958ce6020b
diff --git a/de/heat-templates/env/mstr1-wrkr3-cmp2-gtw0-vsrx1.yaml b/de/heat-templates/env/mstr1-wrkr3-cmp2-gtw0-vsrx1.yaml
index 8871fa3..ff23173 100644
--- a/de/heat-templates/env/mstr1-wrkr3-cmp2-gtw0-vsrx1.yaml
+++ b/de/heat-templates/env/mstr1-wrkr3-cmp2-gtw0-vsrx1.yaml
@@ -11,6 +11,7 @@
 parameters:
   image: bionic-server-cloudimg-amd64-20190612
   public_net_id: public
+  vsrx_image: mos-vsrx-3nets
   masters_size: 0
   worker_size: 3
   cmp_size: 2