lazy-pages: enable lazy-pages via RPC

To use lazy-pages from runc '--lazy-pages' functionality needs to be
accessible via RPC. This enables lazy-pages via RPC.

The information on which port to listen is taken from the
criu_page_server_info protobuf structure. If the user has enabled
lazy-pages via RPC only criu_page_server_info.port is evaluated
to get the listen port.

With additional patches in runc is it possible to use lazy-restore
with 'runc checkpoint' and 'runc restore'.

travis-ci: success for lazy-pages: enable lazy-pages via RPC
Signed-off-by: Adrian Reber <areber@redhat.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>