kanghailin

use less cpu

it may be more graceful to replace this.unRegisterService.shutdown(true) with this.unRegisterService.shutdown()

replacing poll() is better than replacing this.unRegisterService.shutdown() because the queue is empty most of the time

> @kang-hl There is a test shouldBeAbleToRegisterAliasWithNullType that fails with this. I haven't looked deeper but that would indicate null was allowed and thus the changes would break that logic....

> I seemed to recall there was another section with updates...At any rate I don't think the else is necessary and think the first two if statements can be combined...