Remove must-exist: true for mock profile

Change-Id: If9c3a90210d38f6c2daa80844fdc2539eb7c728a
(cherry picked from commit 47a8983f48ddaefeb5fd8a07983069fb02be3258)
diff --git a/roles/cord-profile/templates/mcord-services.yml.j2 b/roles/cord-profile/templates/mcord-services.yml.j2
index a5730d0..40d21ef 100644
--- a/roles/cord-profile/templates/mcord-services.yml.j2
+++ b/roles/cord-profile/templates/mcord-services.yml.j2
@@ -68,7 +68,6 @@
       type: tosca.nodes.Image
       properties:
         name: trusty-server-multi-nic
-        must-exist: true
 
 # management networks, fully created in management-net.yaml
     management: