94-update-smart-drivedb: do not fail on update-smart-drivedb errors

Currently the
http://sourceforge.net/p/smartmontools/code/HEAD/tree/trunk/smartmontools/drivedb.h?format=raw
and related files on sourceforge aren't available and therefor
cause our builds to fail with:

| Updating smartmontool drivedb
| /usr/sbin/update-smart-drivedb: download from trunk failed (HTTP error)

Therefore don't break our builds but instead log a warning
message instead.