MINOR: ShutdownableThread: log on error level on FatalExitError (apache#19351)

This will help debugging the error as the stacktrace is valuable in identifying the origin.

Reviewers: TaiJuWu <[email protected]>, Igor Soarez <[email protected]>, Ken Huang <[email protected]>

Author: gaurav-narula

server-common/src/main/java/org/apache/kafka/server/util/ShutdownableThread.java

@@ -137,7 +137,7 @@ public void run() {
         } catch (FatalExitError e) {
             shutdownInitiated.countDown();
             shutdownComplete.countDown();
-            log.info("Stopped");
+            log.error("Stopped due to fatal error with exit code {}", e.statusCode(), e);
             Exit.exit(e.statusCode());
         } catch (Throwable e) {
             if (isRunning())