Check if pillar 'prometheus:exporters' exists before run state

According to the workflow in the pipeline, prometheus:exporters
is not mandatory state and should run only if the pillar exists.

Change-Id: Iac68b836d92e80846ae50a794496b5bf9c4de678
Reviewed-on: https://review.gerrithub.io/376726
Reviewed-by: Dennis Dmitriev <dis.xcom@gmail.com>
Tested-by: Dennis Dmitriev <dis.xcom@gmail.com>
diff --git a/tcp_tests/templates/virtual-mcp11-k8s-calico/sl.yaml b/tcp_tests/templates/virtual-mcp11-k8s-calico/sl.yaml
index 8309364..3369f63 100644
--- a/tcp_tests/templates/virtual-mcp11-k8s-calico/sl.yaml
+++ b/tcp_tests/templates/virtual-mcp11-k8s-calico/sl.yaml
@@ -56,8 +56,11 @@
   retry: {count: 2, delay: 10}
   skip_fail: false
 
-- description: Configure Prometheus exporters
-  cmd: salt -C 'I@prometheus:exporters' state.sls prometheus
+- description: Configure Prometheus exporters, if pillar 'prometheus:exporters' exists on any server
+  cmd: |
+    if salt -C 'I@prometheus:exporters' match.pillar 'prometheus:exporters' ; then
+      salt -C 'I@prometheus:exporters' state.sls prometheus
+    fi
   node_name: {{ HOSTNAME_CFG01 }}
   retry: {count: 1, delay: 10}
   skip_fail: false