ipfilter: Avoid overrunning the message buffer

Avoid overrunning the message buffer when printing an ippool btree error.
We do this in two ways. First we increase the message buffer from 80 to
255 bytes and secondly we replace strcat(3) with strlcat(3).

(cherry picked from commit 42935716286e7887bfeb9dd8daea72d6a5d40908)