fix variable name

Signed-off-by: zhangzujian <[email protected]>

dist/images/ovn-healthcheck.sh

@@ -34,7 +34,7 @@ fi
 # check nb/sb log file
 function check_log_file() {
     local log_file="/var/log/ovn/ovsdb-server-$1.log"
-    if [ -e $file ]; then
+    if [ -e $log_file ]; then
         logs=$(tail -n 6 $log_file 2>/dev/null || true)
         if echo $logs | grep 'does not match prerequisite' ; then
             echo "raft inconsistency in $1 db was detected, please check $log_file for more details."