fix(dracut): source dracut-functions.sh before calling dwarning

fix(dracut): source dracut-functions.sh before calling dwarning

`dracut-functions.sh` sources `dracut-logger.sh` which defines the
`dwarning` function. `dracut.sh` might call `dwarning` before
`dracut-functions.sh` is sourced.

`dracut-functions.sh` calls `find_binary` and `dlog_init` when sourced.
`find_binary` needs `dracutsysrootdir` set and `dlog_init` needs
`stdloglvl`, `sysloglvl`, `kmsgloglvl`, `maxloglvl`, `fileloglvl`,
`logfile`. Move sourcing `dracut-functions.sh` as early as possible, but
after setting those variables.

Follow-up for 8d9887b
Fixes: https://bugs.debian.org/1124479