Bypass URL doesn't have a corresponding environment variable

[Rick Harris]

Currently if you want to specify a bypass URL, you need to do so with the `--bypass-url` command-line option.

This means if you're doing this repeatedly, each command will need to have the (rather long) `--bypass-url` option included with it.

We should, following the model of other novaclient options, provide a corresponding environment variable that can more permanently set this option so we don't have to specify it on each invocation.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/97622
Committed: https://git.openstack.org/cgit/openstack/python-novaclient/commit/?id=85faf9cbf0de6103c4d4dd7839ea6588eb2c0645
Submitter: Jenkins
Branch: master

commit 85faf9cbf0de6103c4d4dd7839ea6588eb2c0645
Author: Rick Harris <email address hidden>
Date: Tue Jun 3 15:33:15 2014 -0500

    Add NOVACLIENT_BYPASS_URL env variable

    Currently, in order to use a bypass URL, you need to specify it using the
    `--bypass-url` command-line option each time, which is inconvenient if you
    plan on always using a bypass URL.

    This patch adds a `NOVACLIENT_BYPASS_URL` environment variable which can be
    placed in the `novarc` to persistently set this option.

    Change-Id: I49e67ee1fc3570a43e49dc1d78d8ca0b26945bc8
    Closes-Bug: 1326134