Having three booleans in pagemap entry clues for usage of good old flags.
Replace 'zero' and 'lazy' booleans with flags and use flags for internal
tracking of in_parent value. Eventually, in_parent may be deprecated.
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>