V2 shell import fails with schema types []

[Flavio Percoco]

After I75da1e9309e0f7ef8839dea3ec9c99c58edc5d63 landed, some properties in the schema changed their type from bare `string` to either `string` or `null`. The way this is expressed in jsonschema is by adding a list to the `type` attribute in the schema definition.

Our glanceclient, uses the schema returned by the service to introspect the types of some of the properties in the `schema_args` utility. Unfortunately, this function fails for `type` values that are not in the typemap. Furthermore, `lists` are not hashable types, therefore they cannot be used as keys in the typemap.

The `schema_args` function needs to be enhanced to handle the new values returned by the server.

https://github.com/openstack/python-glanceclient/blob/master/glanceclient/common/utils.py#L89

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/140624

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/140624
Committed: https://git.openstack.org/cgit/openstack/python-glanceclient/commit/?id=3989cd202de5d122da011be4f3bb9cede2fe8d45
Submitter: Jenkins
Branch: master

commit 3989cd202de5d122da011be4f3bb9cede2fe8d45
Author: Flavio Percoco <email address hidden>
Date: Wed Dec 10 10:47:40 2014 +0100

    Support schema types with non-str value

    Change I75da1e9309e0f7ef8839dea3ec9c99c58edc5d63 introduced some
    properties' types which are not string. This broke the `schema_args`
    utility since lists are not hashable and there was no support for such
    type values.

    This patch fixes this issue with a very glance specific strategy in
    which this values are assumed to have a `null` type and another type -
    string, integer, etc. The fix ignores `null` options and it takes the
    first non-null type as the valid one.

    The patch adds support for enum types that accept `None`

    Closes-bug: #1401032
    Change-Id: I250e8912aca262a56c54ac59bb24f917e5d8cfce