buildroot

ulogd: forcibly disable mysql when not present

Forcibly disable mysql support when we don't want it since ulogd's
configure script can pick up the host mysql_config thus leading to a
build failure.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>