Eventlet green threads not released back to pool

[OpenStack Infra]

https://review.openstack.org/138811
commit a657582c5cd8a39580c44ad401fd3e69870068b1
Author: abhishekkekane <email address hidden>
Date: Tue Oct 21 01:37:42 2014 -0700

    Eventlet green threads not released back to pool

    Presently, the wsgi server allows persist connections hence even after
    the response is sent to the client, it doesn't close the client socket
    connection.
    Because of this problem, the green thread is not released back to the pool.

    In order to close the client socket connection explicitly after the
    response is sent and read successfully by the client, you simply have to
    set keepalive to False when you create a wsgi server.

    Add a parameter to take advantage of the new(ish) eventlet socket timeout
    behaviour. Allows closing idle client connections after a period of
    time, eg:

    $ time nc localhost 8776
    real 1m0.063s

    Setting 'client_socket_timeout = 0' means do not timeout.

    DocImpact:
    Added wsgi_keep_alive option (default=True).
    Added client_socket_timeout option (default=0).

    Conflicts:
            nova/tests/unit/test_wsgi.py

    Note: The required unit-tests are manually added to the below path,
    as new path for unit-tests is not present in stable/icehouse release.
    nova/tests/compute/test_host_api.py

    This patch is not 1:1 cherry-pick, I have changed the default value
    of client_socket_timeout to 0, as per the policy for changes to
    stable branches.
    (https://wiki.openstack.org/wiki/StableBranch#Appropriate_Fixes)

    SecurityImpact

    Closes-Bug: #1361360
    Change-Id: I399b812f6d452226fd306c423de8dcea8520d2aa
    (cherry picked from commit 04d7a724fdf80db51e73f12c5b8c982db9310742)