Change postgres docker image to alpine

Related-Prod: PROD-36143
Change-Id: Ie41b16b3293837ba8cef94e7b92636212f80e74d
diff --git a/defaults/docker_images.yml b/defaults/docker_images.yml
index 122641d..42d521f 100644
--- a/defaults/docker_images.yml
+++ b/defaults/docker_images.yml
@@ -6,7 +6,7 @@
     docker_image_registry:   "${_param:mcp_docker_registry}/mirantis/external/registry:2019.2.6"
     docker_image_visualizer: "${_param:mcp_docker_registry}/mirantis/external/visualizer:2019.2.6"
     docker_image_openldap: "${_param:mcp_docker_registry}/mirantis/cicd/openldap:2019.2.13"
-    docker_image_postgresql: "${_param:mcp_docker_registry}/mirantis/external/library/postgres:9.6.21"
+    docker_image_postgresql: "${_param:mcp_docker_registry}/mirantis/external/library/postgres:9.6.21-alpine"
     # 3.4.13, from Feb 15, differ from 3.4.13 upstream verison, from March 14 - update next cycle
     docker_image_mongodb: "${_param:mcp_docker_registry}/mirantis/external/mongo:2019.2.6"
     ###
@@ -83,7 +83,7 @@
           name: openldap:2019.2.13
         - registry: ${_param:mcp_docker_registry}/mirantis/external/library
           target_registry: ${_param:default_local_mirrror_content:docker_client_registry_target_registry}/mirantis/external/library
-          name: postgres:9.6.21
+          name: postgres:9.6.21-alpine
         - registry: ${_param:mcp_docker_registry}/mirantis/cicd
           target_registry: ${_param:default_local_mirrror_content:docker_client_registry_target_registry}/mirantis/cicd
           name: phpldapadmin:2019.2.14