Fix deprecated_opts for cli options

The following simple program raises DuplicateOptError.
This commit fixes it.

oslo.config.cfg.DuplicateOptError: duplicate option: argument --bar-foo: conflicting option string(s): --bar-foo

    from oslo.config import cfg

    conf = cfg.ConfigOpts()
    oldopts = [
        cfg.DeprecatedOpt(name='oldfoo', group='oldbar'),
    ]
    conf.register_cli_opt(cfg.StrOpt(name='foo', deprecated_opts=oldopts),
                          group='bar')
    conf()

Change-Id: I022ed0236de97db42568106bc90c696732a05ef2
Closes-Bug: #1283960
Merge "Fix deprecated_opts for cli options"