Make _discover_extensions public

[Andriy Kurilin]

Heat uses[1] `novaclient.shell.OpenStackComputeShell._discover_extensions` function[2], which is private. It means that nova developers can change interface of this method, so heat will be broken(in nova gates).
If heat wants use this method, visibility of it should be changed to public.

[1] - https://github.com/openstack/heat/tree/0a1639a5bcfd0237c988a773885b6c799b89304b/heat/engine/clients/os/nova.py#L59
[2] - https://github.com/openstack/python-novaclient/blob/3681c186f784b0b64f871050a0dfdb3b1bed37b8/novaclient/shell.py#L465

[Ethan Lynn (ethanlynn)]

Is it better to modify novaclient and make this function public? Seems it's the only way to get extensions.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/171067

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/171067
Committed: https://git.openstack.org/cgit/openstack/python-novaclient/commit/?id=02c04c5658dcd968b91f7256b749755abb9d2074
Submitter: Jenkins
Branch: master

commit 02c04c5658dcd968b91f7256b749755abb9d2074
Author: kylin7-sg <email address hidden>
Date: Tue Apr 7 15:23:14 2015 +0800

    Make _discover_extensions public

    Heat uses `novaclient.shell.OpenStackComputeShell._discover_extensions`
    function, which is private currently. It's better to change this method
    to public for public use.

    Change-Id: I15879d56db2ec88a9bef99b6af8924ebd4ad169b
    Closes-bug: #1440779

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/180812