Make ironic-api not single threaded
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

naototty/vagrant-lxc-ironic,NaohiroTamura/ironic,NaohiroTamura/ironic,SauloAislan/ironic,dims/ironic,ionutbalutoiu/ironic,pshchelo/ironic,devananda/ironic,redhat-openstack/ironic,supermari0/ironic,rackerlabs/ironic,froyobin/ironic,openstack/ironic,bacaldwell/ironic,pshchelo/ironic,ramineni/myironic,Tehsmash/ironic,hpproliant/ironic,openstack/ironic,naototty/vagrant-lxc-ironic,Tan0/ironic,debayanray/ironic_backup,JioCloud/ironic,naterh/ironic,dims/ironic,faizan-barmawer/openstack_ironic,ionutbalutoiu/ironic,rdo-management/ironic,varunarya10/ironic,bacaldwell/ironic,SauloAislan/ironic