Introduces eventlet executor for Glance Tasks

[OpenStack Infra]

https://review.openstack.org/44355
commit 186991bb9d2b8c568f3e9a0a89744fd6001ec74a
Author: Nikhil Komawar <email address hidden>
Date: Mon Apr 21 15:13:53 2014 -0400

    Introduces eventlet executor for Glance Tasks

    A sample import script to successfully import image from http or https
    location is introduced. This should work on a devstack installtion.

    Also, the following changes are introduced:-
    1. An interface for implementing any other type of executor.
    2. Provides namespace for keeping Tasks scripts.
    3. A config for choosing deployer specific executor.
    4. An interface for writing Tasks scripts.
    5. A module for common script related methods.
    6. Logic for limiting number of simultaneous tasks execution on the
    Glance API server.

    partially implements bp async-glance-workers
    DocImpact

    Change-Id: I382472fffd0fdad43573e72b2e78a9a6ed1e1f1a

[Andreas Jaeger (jaegerandi)]

Brian, are you still working on this?

[Brian Rosmaita (brian-rosmaita)]

It's on hold at the moment, the architecture for this is most likely changing in K.

[Tom Fifield (fifieldt)]

Options are in CLI-reference, and the arch may have changed - marking fixed