Fix message bus main thread scheduling.
Fix message bus main thread scheduling.

The MessageBus main thread scheduling did not mark the scheduled worker
to be finished, thus main thread items were delivered only once.

peeedge/mobile,ZhangLeiCharles/mobile,eatskolnikov/mobile,peeedge/mobile,eatskolnikov/mobile,ZhangLeiCharles/mobile,eatskolnikov/mobile,masterrr/mobile,masterrr/mobile