use environment variable for running independent tests (units etc.) in ci.rake

git-svn-id: http://svn.redmine.org/redmine/trunk@12437 e93f8b46-1217-0410-a6f0-8f06a7374b81
Fixed that OpenID authentication fails with 422 error due to token verification (#15735).

git-svn-id: http://svn.redmine.org/redmine/trunk@12438 e93f8b46-1217-0410-a6f0-8f06a7374b81