virsh: Fix "positional" argument annotations for 'migrate' command

virsh: Fix "positional" argument annotations for 'migrate' command

Annotate arguments which can be unintentionally parsed positionally.
(See previous commits for explanation.)

Annotate '--migrateuri', '--graphicsuri', '--listen-address', '-dname',
'--timeout', '--xml', '--migrate-disks' and '--disks port' as
'unwanted_positional'. These were declared in chronological order per
git history.

All others are annotated with VSH_OFLAG_REQ_OPT which makes the parser
require the '--optionname'. This is due to the fact that '--disks-uri'
was introduced later and put in front of others declared earlier
breaking the order they would be accepted, thus changing the behaviour
between versions.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>