qemu: set jobinfo type to CANCELLED if migration is cancelled in all conditions

qemu: set jobinfo type to CANCELLED if migration is cancelled in all conditions

The migration job status is traced in qemuMigrationUpdateJobStatus
which is called in qemuMigrationRun. But if migration is cancelled
before the trace such as in qemuMigrationDriveMirror, the jobinfo
type won't be updated to CANCELLED. After this patch, we can get
jobinfo type CANCELLED if migration is cancelled during drive
mirror.  Moreover, we can't use qemuMigrationUpdateJobStatus
because from qemu's point of view it's just the drive mirror being
cancelled and the migration hasn't even started yet.

Signed-off-by: Wang Rui <moon.wangrui@huawei.com>