lazy-pages: make epollfd part of global daemon state

We only use one epoll instance to manage lazy-pages related I/O. Making
epollfd file-visible will allow cleaner implementation of the restored
process exit() calls tracking.

Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>