Comment 1 for bug 1229968

The default extension of '.err' for error log should avoid this.

            find $DATA -mindepth 1 -regex '.*galera.cache$\|.*sst_in_progress$\|.*grastate.dat$\|.*err$' -prune -o -exec rm -rfv {} 1>&2 \+

is the command used to remove.

Only other alternative is to make this pattern configurable from my.cnf.