bitlbee: Adjust permissions of ${VARBASE}/run/bitlbee

Similarly to ${STATEDIR}, ${VARBASE}/run/bitlbee should be owned by
bitlbee:nobody.

This fixes the case when bitlbee is started in daemon mode (via
rc.d/bitlbee) as `bitlbee' User. Now `service bitlbee start|stop'
works properly (previously the pidfile wasn't created in that case).

Approved by <tonio>, thanks!

(leot)