Use BUILD_NUMBER for docker image tag instead of BUILD_ID (#4701)
Use BUILD_NUMBER for docker image tag instead of BUILD_ID (#4701)

This solves an issue when the branch name includes characters that
aren't valid docker image tags, such as

http://jenkins.vetsgov-internal/blue/organizations/jenkins/department-of-veterans-affairs%2Fvets-website/detail/content%2Fwip%2Feducation-plain-language-update/3/pipeline
department-of-veterans-affairs/vets-website,department-of-veterans-affairs/vets-website