tools/libxl: optimize domain creation skipping domain cpupool move

tools/libxl: optimize domain creation skipping domain cpupool move

Commit 92ea9c54fc81 ("arm/dom0less: assign dom0less guests to cpupools")
introduced a way to start a domain directly on a certain cpupool,
adding a "cpupool_id" member to struct xen_domctl_createdomain.

This was done to be able to start dom0less guests in different pools than
cpupool0, but the toolstack can benefit from it because it can now use
the struct member directly instead of creating the guest in cpupool0
and then moving it to the target cpupool.

Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Luca Fancellu <luca.fancellu@arm.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Acked-by: Anthony PERARD <anthony.perard@citrix.com>