Revert "Use absolute path /usr/bin/dracut in mkdumprd"

This reverts commit 8e3b6475c9.

After reading the background of bugzilla:
https://bugzilla.redhat.com/show_bug.cgi?id=1510922

It is not a problem actually, sorry for the noise.

Although root set different "PATH" can lead to wrong script, but it is
different with what the bug described "current working dir" and it is
not a problem worth an update

mkdumprd

@@ -17,7 +17,6 @@ SAVE_PATH=$(grep ^path $conf_file| cut -d' '  -f2)
 [ -z "$SAVE_PATH" ] && SAVE_PATH=$DEFAULT_PATH
 # strip the duplicated "/"
 SAVE_PATH=$(echo $SAVE_PATH | tr -s /)
-DRACUT_PATH=/usr/bin
 
 is_wdt_addition_needed() {
 	local active
@@ -458,7 +457,7 @@ if ! is_fadump_capable; then
     add_dracut_arg "--no-hostonly-default-device"
 fi
 
-${DRACUT_PATH}/dracut "${dracut_args[@]}" "$@"
+dracut "${dracut_args[@]}" "$@"
 _rc=$?
 sync
 exit $_rc