virsh: Annotate '--diskspec' _ARGV options as unwanted positional

Our documentation in most places explicitly mentions --diskspec and it
was never meant to be positional, although we can't change the parser
any more. Annotate them as 'unwanted_positional'.

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

tools/virsh-checkpoint.c

@@ -206,6 +206,7 @@ static const vshCmdOptDef opts_checkpoint_create_as[] = {
     },
     {.name = "diskspec",
      .type = VSH_OT_ARGV,
+     .unwanted_positional = true,
      .help = N_("disk attributes: disk[,checkpoint=type][,bitmap=name]")
     },
     {.name = NULL}