add test rule

git-svn-id: https://svn.apache.org/repos/asf/spamassassin/trunk@1637046 13f79535-47bb-0310-9956-ffa450edef68
FP avoidance tuning

git-svn-id: https://svn.apache.org/repos/asf/spamassassin/trunk@1637047 13f79535-47bb-0310-9956-ffa450edef68