Regression in VCS behavior under high load / concurrency break the integration tests on master

For instance:

https://qa.nuxeo.org/jenkins/view/5.7/job/IT-nuxeo-drive-master-linux/71/console

is broken (8 errors and 8 failures) as the filename of a blob uploaded via automation and stored in VCS is not the same requested in the original HTTP request. It seems that this problem does not happen when the HTTP requests are not as frequent as when running integration tests. So it might reveal a concurrency issue in either VCS or in automation.

This problem was never observed on the 5.6 branch and is not reproducible on a SDK of 2013-01-22 so it might have been caused by changes in VCS that impact the concurrency handling of asynchronous tasks.