Satori should provide a way to override Popen

[Ryan Walker]

Currently smb.py and bash.py both use subprocess.Popen. subprocess.Popen utilizes os.fork() to spawn child processes. If the process calling smb.py or bash.py has a large memory footprint, os.fork() performs very slowly due to memory allocation. It would be better for Satori to call Popen in a way that allowed a calling application to override the underlying Popen process to use something like posix_spawn instead for better performance.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/148714

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/148714
Committed: https://git.openstack.org/cgit/stackforge/satori/commit/?id=fd350f7f1c4da7c5dd5b925d77646a3cea27619b
Submitter: Jenkins
Branch: master

commit fd350f7f1c4da7c5dd5b925d77646a3cea27619b
Author: Ryan Walker <email address hidden>
Date: Mon Jan 19 11:28:04 2015 -0600

    Refactor Popen usage to allow overrides

    * Add subprocess.Popen wrapper in common
    * Change bash.py and smb.py to use wrapper.

    Because subprocess.Popen uses os.fork() to spawn child processes, it may
    be desirable for a calling application to override subprocess.Popen with
    a custom class that implements a different spawning method - such as
    posix_spawn. With large-memory applications, posix_spawn may be more
    desirable than os.fork() due to memory allocation behavior. This change
    allows Satori to be compatible with such a workflow.

    Change-Id: Ia60adea27d1a6cbf28341ea3aece5ee604a94583
    Closes-Bug: #1412485