Bug#47612 mtr - improving the report for valgrind erorrs

- Improve the report produced when a valgrind error is detected

mysql-test/include/check-warnings.test

@@ -57,5 +57,5 @@ if (`select @result = 0`){
   skip OK;
 }
 --enable_query_log
-echo ^ Found warnings!!;
+echo ^ Found warnings in $log_error!!;
 exit;

mysql-test/include/mtr_warnings.sql

@@ -207,7 +207,7 @@ BEGIN
     WHERE suspicious=1;
 
   IF @num_warnings > 0 THEN
-    SELECT file_name, line
+    SELECT line
         FROM error_log WHERE suspicious=1;
     --SELECT * FROM test_suppressions;
     -- Return 2 -> check failed