CBSP VTY: re-add legacy cbc config for backwards compat

In commit [1], I replaced the way the CBSP link is configured in the VTY. But
that configuration was already part of a release, hence I should only have
deprecated the old commands. Re-add the legacy config as deprecated.

Try to make the legacy commands take a similar effect as they previously would
be intended for, i.e. switching to server/client/disabled modes, and take
effect immediately when commands are read from telnet.

[1] 641f7f08450f2d0c4b8e8a9f6a36b0a6b2788816
    Icaa2775cc20a99227dabe38a775ff808b374cf98
    "CBSP: rewrite the CBSP link setup and 'cbc' VTY section"

Related: OS#4702
Change-Id: If6b742f28191b3f19ff1d87a217037a305133f4b
2 files changed