CBLT-254:  env.vars are now MVN_UPLOAD_USERNAME, MVN_UPLOAD_PASSWORD

Change-Id: Ibb38d8e89a04f93a9a7f5147256806a9ceffe9b9
Reviewed-on: http://review.couchbase.org/35535
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>