benchmarks: clean up infra logs (#15198)

The response from curl could contain secrets for the test
ephimeral cluster. There is no need to display it unless
an error occurred, when we may need it for debugging purposes.

testing/infra/terraform/modules/ec_deployment/scripts/enable_features.tftpl

@@ -23,7 +23,10 @@ echo $${POLICY} | jq '.item' | \
     jq 'select(.inputs[].policy_template == "apmserver").inputs[].vars.tail_sampling_storage_limit = {"value":"${tail_sampling_storage_limit}","type":"text"}' |\
     jq 'select(.inputs[].policy_template == "apmserver").inputs[].vars.tail_sampling_enabled = {type: "bool", value: ${enable_tail_sampling}}' > policy.json
 
-# Update the policy
-curl -s -H 'content-type: application/json' -H 'kbn-xsrf: true' -X PUT -k [email protected] -u $${KIBANA_AUTH} $${KIBANA_ENDPOINT}
+# Update the policy, hide output to prevent secret leakage.
+if ! curl -s -o response.txt -H 'content-type: application/json' -H 'kbn-xsrf: true' -X PUT -k [email protected] -u $${KIBANA_AUTH} $${KIBANA_ENDPOINT}; then
+  # If command failed print output to aid troubleshooting.
+  cat response.txt
+fi
 
 rm -f policy.json