* If select created a spurious wakeup (probably only theoretical problem
  on unix domain socket), it could block indefinitely.
* Eliminated race condition on fast start-shutdown serie
* Made the run_timers()-shutdown() be callable multiple times
* Fixed a shutdown problem with empty zone manager (it didn't get to
  select when there were no data)

git-svn-id: svn://bind10.isc.org/svn/bind10/branches/trac335@3191 e5f2f494-b856-4b98-b285-d166d9295462