Fix commit b7731f39 that inversed order of timing functions

Fix commit b7731f39 that reverse order between distributed synchronization and timer start/stop.

The timer must be started once all the processes have been synchronized and stopped once all processes are done with all the computation, so again, after processes synchronization.

@fpruvost, @agullo, @sthibault: please review I didn't do any mistake, and I'll merge it quickly.

@thibault who put an expiration date on your Chameleon membership !!! :D.

Thanks @faverge for the fix and thanks Thomas H. for the catch!

merged

mentioned in commit 75ed3157

mentioned in merge request !55 (merged)