ZOOKEEPER-4837: Network issue causes ephemeral node unremoved after t…

[dParikesit]

…he session expiration

The core part of this fix is

// if this snapshot has a higher zxid than the checkpoint zxid, skip and continue to the previous snapshot
if (snapZxid > zxid) {
    continue;
}

However, the zxid must be propagated from tuncateLog(), which is why I added another loadDatabase, deserialize, and restore with zxid as its additional parameter.