There was a 'capbilities' typo in this man page. This commit
reformulates the sentence the typo was in to make it easier to grasp.
This is based on a suggestion from Eric Blake.

Signed-off-by: Christophe Fergeau <cfergeau@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>