zdtm.py: postpone waiting for lazy-pages daemon

Currently we are waiting for lazy-pages daemon to finish as a part of
.restore method, which may cause filling test process memory before the
test process resumed it's execution after call to test_waitsig(). In such
case, no page faults occur, but rather all the memory is copied in
handle_remaining_pages method in uffd.c.
Let's move wait(<lazy-pages-pid>,..) after call to test.stop().

travis-ci: success for lazy-pages: add non-#PF events handling
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>