registration_ip is not long enough in some cases

In some cases as the [post](https://stackoverflow.com/questions/31100703/stripping-ffff-prefix-from-request-connection-remoteaddress-nodejs) mentioned, the `registration_ip` will be IPv4-mapped IPv6 address format, like `::ffff:aaa.bbb.ccc.ddd` which exceeds the definition of the `registration_ip` in DB (which is STRING(20)) and causes all `registration_ip` related api failed.