scm: git: change "decorate = short" to "decorate = no" in config log section of test repository (#8081, #8083).

Git on Redmine CI Server does not support "--no-decorate" option of "git log".

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@5348 e93f8b46-1217-0410-a6f0-8f06a7374b81