Interactive mode and other improvements to vasum-cli tool

Interactive mode and other improvements to vasum-cli tool

[Feature]       These features have been implemented/updated:
                - interactive mode
                - persistent connection during interactive mode
                - better help
                - simple mode for cli auto-completion
                The interactive mode allows to make full use of queue
                lock/unlock commands. They can also be easily tested
                with it.
[Cause]         n/a
[Solution]      n/a
[Verification]  Run vasum-cli and executed several commands.
                Tested auto completion. Tested lock/unlock queue.

Change-Id: If623559c9250bf480cc600ba89c2d5fe02137a18