Accidentally syncing from two computers (because mutex is not checked correctly)

[rodja]

With the following scenario two computers sync their code changes to the same target and break our assumption of exclusivity:

1. start LiveSync on computer A
2. put computer A in power save mode
3. wait 10 seconds (so the lock on the target expires)
4. start LiveSync on computer B
5. wake computer A from power safe

-> now computer A and B both sync to the target because A assumes it still has the lock