libceph: correctly decode ADDR2 addresses in incremental OSD maps

Given the new format, we have to decode the addresses twice. Once to
skip past the new_up_client field, and a second time to collect the
addresses.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>