wicket/wicketd: expose a way to abort an in-progress update on the SP

Updates on the SP are relatively stateful: if we've started an update to (e.g.) the host-boot-flash, no other updates can be started until that update either finishes or is aborted, or the SP is restarted. Today, there is no way from wicket to explicitly restart the SP or abort an in-progress-from-the-SP's-point-of-view update. To do this by hand, we can use faux-mgs:

update-status COMPONENT

will print the status and a UUID of the update, then

update-abort COMPONENT UUID

will abort the update.

In the worst case, we do have ignition control exposed in wicket, but it would be good to use the more graceful cleanup methods if we could.

Start by tracing wicket/wicketd's existing update handling and the exposed ignition-control path, then compare how faux-mgs uses update-status and update-abort for a component. Done means wicket provides a graceful way to identify and abort an in-progress SP update without restarting the SP.