Use the 18.04 image as the base image for ci-management jobs

- Get rid of the Centos and ubuntu 16.04
- Keep all packer files for ubuntu 16.04 until we migrated all jobs to
ubuntu 18.04

Change-Id: I8d87a6352819c3bfb71259413391f70f7943575e
diff --git a/jjb/ci-management/ci-management.yaml b/jjb/ci-management/ci-management.yaml
index 476e37b..f73d9b5 100644
--- a/jjb/ci-management/ci-management.yaml
+++ b/jjb/ci-management/ci-management.yaml
@@ -3,20 +3,13 @@
     archive-artifacts: '**/*.log'
     branch: 'master'
     build-timeout: '60'
-    build-node: 'centos7-basebuild-1c-1g'
+    build-node: 'ubuntu18.04-basebuild-1c-1g'
 
     jobs:
       - '{project-name}-ci-jobs'
-      - '{project-name}-packer-jobs':
-          platforms:
-            - 'centos-7'
-            - 'ubuntu-16.04'
-          templates:
-            - basebuild
 
     name: ci-management-jobs
     project: 'ci-management'
     project-name: 'ci-management'
 
     jjb-version: 3.2.0
-    packer-version: 1.2.4