`console log show xxx` broke without `--lines` option

[xyj]

Error seen:

(openstack) console log show bf871e90-0850-4f1d-a770-3126c1beb560
ERROR: cliff.app unsupported operand type(s) for +: 'NoneType' and 'int'

Reason:

The parser defaults the lines variable to None.

        parser.add_argument(
            '--lines',
            metavar='<num-lines>',
            type=int,
            default=None,
            help='Number of lines to display from the end of the log '
                 '(default=all)',
        )

However we end up trying to add an int value of 1 in some cases.

        data = server.get_console_output(length=parsed_args.lines + 1)

[Openstack Gerrit (openstack-gerrit)]

Fix proposed to branch: master
Review: https://review.openstack.org/92501

[Openstack Gerrit (openstack-gerrit)]

Reviewed: https://review.openstack.org/92501
Committed: https://git.openstack.org/cgit/openstack/python-openstackclient/commit/?id=3b57117f8efc0c945f730c5e8a598768ac774114
Submitter: Jenkins
Branch: master

commit 3b57117f8efc0c945f730c5e8a598768ac774114
Author: Yejia Xu <email address hidden>
Date: Wed May 7 01:49:15 2014 +0000

    Display all server log when --lines option is None

    Without --lines option, `console log show xxx`
    cmd will break.

    Change-Id: I4027aacac245e6916c1808fd9f878fb708c8a5f0
    Closes-Bug: #1316870