Restore of a zombie process does not call setup_uffd which causes
lazy-pages daemon to stuck forever waiting for (pid, uffd) pair to arrive.
Let's extend the protocol between restore and lazy-pages so that for zombie
process a (0, -1) pair will be sent instead of actual (uffd, pid).

travis-ci: success for lazy-pages: misc fixes (rev4)
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>