Upgrade ONOS to 1.12.0.

Change-Id: I9abcc7c57ffd2e70e6d417888e63181f464d14c9
diff --git a/docker_images.yml b/docker_images.yml
index 0a8aacc..1783f62 100644
--- a/docker_images.yml
+++ b/docker_images.yml
@@ -30,7 +30,7 @@
   - "gliderlabs/consul-server:0.6"
   - "gliderlabs/registrator:v7"
   - "nginx:1.13"
-  - "onosproject/onos:1.10.10"
+  - "onosproject/onos:1.12.0"
   - "redis:3.2"
   - "node:7.9.0" # remove once the issue with node:candidate is resolved
   - "sebp/elk:564"