Ensure 90rkhunter does not generate an error by adding '|| true' (closes #993748)

Ensure 90rkhunter does not generate an error by adding '|| true' (closes #993748)

See https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=993748 this can be an issue due without usrmerge and would seem a sensible precaution anyway