Bump CS_MAJOR_VERSION from 1 to 2

- Version 1 of the Container Scanning tool
  produced a report using the format specified by
  clair-scanner (github.com/arminc/clair-scanner),
  however, version 2 of the Container Scanning
  tool now produces a report using the GitLab
  Analyzers Common Library Format.  In order to
  make use of the new report format, we need to
  update the CS_MAJOR_VERSION.

lib/gitlab/ci/templates/Security/Container-Scanning.gitlab-ci.yml

 # Read more about this feature here: https://docs.gitlab.com/ee/user/application_security/container_scanning/
 
 variables:
-  CS_MAJOR_VERSION: 1
+  CS_MAJOR_VERSION: 2
 
 container_scanning:
   stage: test