Use ironic's bash-completion for CLI commands

This removes the list of ironic subcommands. Ironic now has a bash-completion
subcommand, and that will be used instead, to generate the list of subcommands.

Change-Id: I5adcbc8f755f6031ddc122205203ccfcedcf7a15
Closes-Bug: #1367333
Merge "Use ironic's bash-completion for CLI commands"