Move eventlent monkeypatch out of cmd/

Completing a #TODO that I left for myself months ago,
now that we are using PBR for our build system,
move the eventlent monkey patching out of ironic/cmd/__init__
and into ironic/__init__

Change-Id: I1fd352919de0a2afe7058ab84c208781ce095dab
Make ironic-api not single threaded

The ironic-api service is an instance of wsgiref
simple_server.WSGIServer.  This derives from SocketServer.TCPServer,
which requires that SocketServer.ThreadingMixIn be mixed in for it to
become thread'able, however this was not being done when starting the
WSGIServer.

This patch creates a ThreadedSimpleServer class, which is just a mix
of ThreadingMixIn and WSGIServer, so that the ironic-api process
does not block on network IO.

Change-Id: I9d686765edb4975519840a51d3beeb2be797a4fa
Related-bug: #1279206
Fix task_manager acquire post landing for c4f2f26ed

In original implementation we used context lib with try/finally
to make sure release_resources will be called even if there was an
exception inside acquire_resources. With c4f2f26ed we broke that
functionality, so this patch intended to fix this.

Closes-Bug: #1279992
Change-Id: I04abc67aedc226bc126b1d93901c71bcd8a5bf15
Merge "Make ironic-api not single threaded"
Merge "Move eventlent monkeypatch out of cmd/"