test459: fix for parallel runs

- change warniing message to work better with varying filename
  length.
- adapt test output check to new formatting

Follow-up to 97ccc4479f
Closes #12423

src/tool_parsecfg.c

@@ -210,9 +210,9 @@ int parseconfig(const char *filename, struct GlobalConfig *global)
             break;
           default:
             warnf(operation->global, "%s:%d: warning: '%s' uses unquoted "
-                  "whitespace that may cause side-effects. Consider quoting "
-                  "the value with double quotes?",
-                  filename, lineno, option);
+                  "whitespace", filename, lineno, option);
+            warnf(operation->global, "This may cause side-effects. "
+                  "Consider using double quotes?");
           }
         }
         if(!*param)