This change:
* avoids creating lots of short-lived threads
(because: why would we ?)
* adds a try/except block to be sure we can log
any issue that would otherwise be hidden by
spawn_n.
* changes class from Queue to LightQueue after
eventlet.queue code inspection, since it's a
little smaller and should be faster
Change-Id: Ic348c08af375099a919116188ae17d2017695ecb
Closes-Bug: 1750777
(cherry picked from commit 35c225aaa3)