## What changes were proposed in this pull request?

This expands calls to Jetty's simple `ServerConnector` constructor to explicitly specify a `ScheduledExecutorScheduler` that makes daemon threads. It should otherwise result in exactly the same configuration, because the other args are copied from the constructor that is currently called.

(I'm not sure we should change the Hive Thriftserver impl, but I did anyway.)

This also adds `sc.stop()` to the quick start guide example.

## How was this patch tested?

Existing tests; _pending_ at least manual verification of the fix.

Author: Sean Owen <sowen@cloudera.com>

Closes #15381 from srowen/SPARK-17707.