bogofilter: set BOGOFILTER_DIR to /etc/bogofilter, as /var/lib is wiped on reboot

Signed-off-by: W. Michael Petullo <mike@flyn.org>
Merge pull request #489 from MikePetullo/master

bogofilter: set BOGOFILTER_DIR to /etc/bogofilter, as /var/lib is wiped ...