Parser.listing method return empty list if env doesn't have resources,
so assertTableStruct works wrong, doesn't check field names in the
output table.

This change add new assert(assertTableHeaders) to check resource
attributes.

Change-Id: Ieca67b5cc2202467527c5a2dfbd7b2f2b4d5ad8d
Closes-Bug: #1458932

With the recent update to tox 2.0.x, environment variables such as
OS_AUTH_URL are not passed by default, resulting in tests errors
mentionning Keystone authentication failures.

This patch reads credentials from the 'functional_creds.conf' config
file, like it is done in novaclient (and soon in glanceclient and
neutronclient).

Reading credentials the old way (the environment) is still possible.

Change-Id: I2ec1df481aba7a3866fc8dbc912311de02c22d11
Related-Bug: #1455102

This is an initial add of a simple post_test_hook for the
functional tests that are run in cinderclient.

Change-Id: If0b242c4caaa611da8fb55b8f04ab436c0ce9984

First pass at functional tests in cinderclient.  This patch
just takes some of the basic CLI tests from tempest and moves
them into the cinderclient functional tests.

These are read-only tests, and just do simple field checks
on the tables generated by the basic list commands.

Note: to run use "tox -efunctional", this requires that you
have a full cinderclient env and credentials are set. You may
be either running this locally (say in a devstack env) or
you may have a remote cloud handy that you can just source the
credentials for and run it that way.

Change-Id: I2f09a63be265d6a74cb103d80579068b9ab66bf4