Merge pull request #4 from Kegeruneku/master

Fixes #4376: Add rudder-sync.sh to the utility scripts (Thanks dnns !)
Remove branch 2.4 from repo-merge.sh
Remove branch 2.4 and add branch 2.9 from update branches script
Update repo-merge.sh since 2.7 is not supported anymore
Fix update all branches script ( rm 2.4 2.7 add 2.9)