Without non-cooperative userfaultfd some programs may fail during lazy
restore because they perform operations that cannot be handled by the
lazy-pages daemon.

✓ travis-ci: success for lazy-pages: update checks for availability of userfaultfd (rev3)
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>