etc/comp_channel: fix lost event problem

etc/comp_channel: fix lost event problem

The previous version of the completion channel was racy and would
occasionally lose events, resulting in users blocking indefinitely
if no new events occurred.  The most sure fix for this is to add
a thread to the completion manager that reaps events from an IO
completion port and dispatches them to the correct completion
channel.  This results in a 1-2% performance hit in libibverbs
bandwidth tests that wait on CQ, but actually works.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>
git-svn-id: svn://openib.tc.cornell.edu/gen1@2127 ad392aa1-c5ef-ae45-8dd8-e69d62a5ef86