Improve error logging for spark test crashes

While working on HIVE-7665, I noticed that spark local cluster will crash entire JVM on any dependency version mismatch, either due to native code linkage errors if you are unlucky, or gracefully (see spark's ExecutorUncaughtExceptionHandler.scala) most of the time.

To debug those issues, it would be nice to log a thread-dump upon normal JVM exits by spark by ExecutorUncaughtExceptionHandler, as its unexpected by Hive's test framework. One way is to add a shutdownHook that does this.