virt-admin: Annodate 'unwanted_positional' arguments

virt-admin: Annodate 'unwanted_positional' arguments

Historically the command parser in virsh parses/fills even optional
arguments with values as if they were positional unless opted out using
VSH_OFLAG_REQ_OPT. This creates unexpected situations when commands can
break in this unwanted semantics:

 $ virsh snapshot-create-as --print-xml 1 2 3
 <domainsnapshot>
   <name>2</name>
   <description>3</description>
 </domainsnapshot>

To prevent any further addition annotate the rest of the arguments with
the 'unwanted_positional' flag, so that the parser can keep parsing them
as such but any further optional argument will not have this behaviour.

Certain arguments where it makes sense are annotated as 'positional' too
in this patch.

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