Fixed a regression in d92fb7fbcc34b7bf6b1649befab1d9eafec13684: We must not close...

Fixed a regression in d92fb7fbcc34b7bf6b1649befab1d9eafec13684: We must not close the handle to the Job Object, as long as there still might be a process "tool" running. The regression caused child processes to be terminated unexpectedly sometimes! We now use reference counting in order to avoid this problem.