Set prom-es-exporter image tag to 2019.2.6

Change-Id: Ib406c806af7ac28c5ad0c5803b9a1c01559f2f8d
Related-bug: PROD-32451
diff --git a/defaults/docker_images.yml b/defaults/docker_images.yml
index fcd8590..166f273 100644
--- a/defaults/docker_images.yml
+++ b/defaults/docker_images.yml
@@ -31,7 +31,7 @@
     docker_image_alerta: "${_param:mcp_docker_registry}/mirantis/external/alerta-web:${_param:mcp_version}"
     docker_image_alertmanager: "${_param:mcp_docker_registry}/openstack-docker/alertmanager:2019.2.4"
     docker_image_grafana: "${_param:mcp_docker_registry}/openstack-docker/grafana:${_param:mcp_version}"
-    docker_image_prometheus_es_exporter: "${_param:mcp_docker_registry}/openstack-docker/prometheus-es-exporter:2019.2.4"
+    docker_image_prometheus_es_exporter: "${_param:mcp_docker_registry}/openstack-docker/prometheus-es-exporter:2019.2.6"
     docker_image_prometheus: "${_param:mcp_docker_registry}/openstack-docker/prometheus:${_param:mcp_version}"
     docker_image_prometheus_gainsight: "${_param:mcp_docker_registry}/openstack-docker/gainsight:2019.2.4"
     docker_image_prometheus_gainsight_elasticsearch: "${_param:mcp_docker_registry}/openstack-docker/gainsight_elasticsearch:${_param:mcp_version}"