lazy-pages: do not treat VMAs that have MAP_LOCKED as lazy

When a VMA is mapped with MAP_LOCKED it is address space is populated with
pages which causes UFFDIO_COPY to return -EXISTS. Until we can find some
better solution let's avoid marking VMAs with MAP_LOCKED as lazy.

Fixes: #238

travis-ci: success for lazy-pages: misc fixes (rev3)
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>