Fix examples to work with QuickStart VM 5.1

While working on migrating the demo, logging, and logging-webapp examples to use Flume's Log4jAppender and DatasetSink in CDK-647, I ran into a number of issues with the CDH5.1 QuickStart VM. Most of them stem from two changes:

• The default hostname is not quickstart.cloudera
• The use of YARN/MR2 versus MR1

The rest of the examples need to be checked and updated as necessary. We also need to confirm the steps for running from a third-party system against a "remote" QuickStart VM.