Clang: fix cancellation of CreateMarkers.

Also call reportFinished(), so waitForFinished() will actually return.

Change-Id: I65110b3d735ae89031e3d09252006f072f573d98
Reviewed-by: Sergey Shambir <sergey.shambir.auto@gmail.com>
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>