dracut-logger: prefix stderr output with "dracut: "

dnf updates of the kernel execute dracut in %post.
For the user it is not possible to distinguish the dracut output from
other error messages.

dracut-logger.sh

@@ -324,7 +324,7 @@ _do_dlog() {
     local msg="$*"
     local lmsg="$lvlc: $*"
 
-    (( $lvl <= $stdloglvl )) && echo "$msg" >&2
+    (( $lvl <= $stdloglvl )) && printf -- 'dracut: %s\n' "$msg" >&2
 
     if (( $lvl <= $sysloglvl )); then
         if [[ "$_dlogfd" ]]; then