[ACS4.4] Cherry-pick e3bb8b98bd9055115004da2ec67b29271a3974c5

[Kelven Yang]

There is an typo on the bug id, it should be the fix for CLOUDSTACK-6743

commit e3bb8b98bd9055115004da2ec67b29271a3974c5
Author: Kelven Yang <kelv...@gmail.com>
Date:   Wed May 21 16:14:14 2014 -0700

    CLOUDSTACK-5485: Use edge-triggering in MessageDetector to handle
bogus wakeup gracefully. Level triggering plus bogus wakeup can cause a
tight loop to spin

Thanks
Kelven