dabbad: don't create a pidfile when not requested.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
dabbad: remove default pidfile path definition.

It has no place here. /etc/init.d/dabba script must precise where the
pidfile must be created.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>