NAS-Filter-Rule incorrectly encoded as string

[Alan DeKok]

  FYI I've pushed changes to v3 which will automatically do this for 3.0.22 (when that's released)

https://github.com/FreeRADIUS/freeradius-server/commit/310083864657543a8968f10beff90e971fc2fb4d

  Alan DeKok.