Docker conductor wrap exception incorrectly

[hongbin]

In file magnum/conductor/handlers/docker_conductor.py, several methods are double-wrapping exceptions. For example:

* First wrap:
In method container_delete:
        except errors.APIError as api_error:
            raise exception.ContainerException(
                "Docker API Error : %s" % str(api_error))

* Second wrap:
In method wrap_container_exception:
            raise exception.ContainerException(
                "Docker internal Error: %s" % str(e))

The double-wrapping results in lost of information.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/227552

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/227552
Committed: https://git.openstack.org/cgit/openstack/magnum/commit/?id=0d3a3035edd60b6129f121dd8c6de724f2b9736b
Submitter: Jenkins
Branch: master

commit 0d3a3035edd60b6129f121dd8c6de724f2b9736b
Author: Hongbin Lu <email address hidden>
Date: Thu Sep 24 16:48:35 2015 -0400

    Fix double-wrapping of exception in conductor

    In docker conductor, ContainerException are double-wrapped. In
    particular, methods with decorator @wrap_container_exception should
    not wrap a native exception into Container exception, since the
    decorator will wrap it again.

    Change-Id: If85db06c8bbee6bd58fde9ece13a4cc523e58e2d
    Closes-Bug: #1499524