HBASE-28345 Close HBase connection on exit from HBase Shell

Author: stoty

hbase-shell/src/main/ruby/shell.rb

@@ -108,6 +108,8 @@ class Shell
     # exit the interactive shell and save that this
     # happend via a call to exit
     def exit(ret = 0)
+      # Non-deamon Netty threadpool in ZK ClientCnxnSocketNetty cannot be shut down otherwise
+      self.hbase.shutdown
       @exit_code = ret
       IRB.irb_exit(IRB.CurrentContext.irb, ret)
     end