formatcaps: Update capabilities example

formatcaps: Update capabilities example

In the formatcaps.rst we give an example output of capabilities.
Well, there are couple of issues with it:

1) We show <features/> nested under /capabilities/host/cpu.
   There's no such element and never was.

2) The ordering of elements is corrupted.

3) There is plenty of elements missing.

Fix these by showing an actual output of 'virsh capabilities' as
obtained on my machine.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>