Parameterizes webhook service URL as env variable

Signed-off-by: garciaale <agarcia@whitestack.com>

cirros_alarm_vnf/cirros_alarm_vnfd.yaml

@@ -29,11 +29,11 @@ vnfd-catalog:
                 value: 20
                 actions:
                   alarm:
-                    - url: https://webhook.site/e65ad8a0-53b5-4d7f-bd50-c1a50b260871 
+                    - url: ${WEBHOOK_URL} 
                   ok:
-                    - url: https://webhook.site/e65ad8a0-53b5-4d7f-bd50-c1a50b260871
+                    - url: ${WEBHOOK_URL}
                   insufficient-data:
-                    - url: https://webhook.site/e65ad8a0-53b5-4d7f-bd50-c1a50b260871
+                    - url: ${WEBHOOK_URL}
                 vnf-monitoring-param-ref: cirros_vnf_cpu_util
             count: 1
             description: cirros_vnfd-VM