HttpServer.stop seems to wait longer than expected

[Pavel Rappo]

The specification of the method has these words (emphasis mine):

> The method will then block until all current exchange handlers have completed or else when approximately delay seconds have elapsed (__whichever happens sooner__).

I noticed that stop(t) blocks for approximately `t` seconds regardless
of whether there are any handlers being executed at the same time. I
thought that if there are no handlers being executed, `stop` would
return immediately. Did I misread the spec?

-Pavel