Rails3: test: scm: add "repository_path_hash" method in test_helper.rb for common use

Rails3 new route format returns path param as string not array.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@8923 e93f8b46-1217-0410-a6f0-8f06a7374b81