[CORD-2889]
Change to using premade `postgres` container

Change-Id: I3f4dc65d7b6957cbd9b8b7d5d3dc23045d4b1a82
diff --git a/docker_images.yml b/docker_images.yml
index f7ec2b6..75a41b6 100644
--- a/docker_images.yml
+++ b/docker_images.yml
@@ -31,6 +31,7 @@
   - "onosproject/onos:1.12.0"
   - "redis:3.2"
   - "node:7.9.0" # remove once the issue with node:candidate is resolved
+  - "postgres:10.3-alpine"
   - "sebp/elk:564"
 
 # buildable_images - list of images that we build from Dockerfiles