Align ServerPush implementation with Executions.schedule JavaDoc

From Executions.schedule java doc:
"Schedules a task to run under the server push of the given desktop asynchronously"

In current implementation, when Execution.schedule is call from event listener, task is post to the end of the current event queue and will be called by the same event processing thread, i.e not run asynchronously in a separate thread. This is not inline with the method's documentation.