ulogd: fix build failure

Fix Peter's reported build failure:
http://autobuild.buildroot.net/results/1dcf63799937f2216e3c712af8880ad431dbd47c/build-end.log


This is because the configure script uses absolute paths to detect dbi,
mysql and pgsql, so forcibly disable them.
Also add the optional sqlite dependency when it's selected.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>