Re: [libvirt] [PATCH] qemu: track 'cancelling' migration state

In qemu 2.3, the migration status will include 'cancelling' in the window between when an asynchronous cancel has been requested and when the migration is actually halted. Previously, qemu hid this state and reported 'active'. Libvirt manages the sequence okay even when the string is unrecognized (that is, it will report an unknown state: Migration: [ 69 %]^Cerror: internal error: unexpected migration status in cancelling. but the migration is still cancelled), but recognizing the string makes for a smoother user experience.