dbus: put local state files in /var and not /usr/var

For read only rootfs'es - Like it used to be.

package/dbus/dbus.mk

@@ -29,6 +29,7 @@ DBUS_CONF_OPT = --program-prefix="" \
 		--disable-doxygen-docs \
 		--disable-static \
 		--enable-dnotify \
+		--localstatedir=/var \
 		--with-system-socket=/var/run/dbus/system_bus_socket \
 		--with-system-pid-file=/var/run/messagebus.pid