CDK-647: Update examples to use Flume's Log4jAppender and DatasetSink

 * This patch includes configuring the Log4jAppender to gracefully
    handle connection errors. This is useful as it avoids a circular
    dependency between loading the log4j configuration to create the
    dataset and starting Flume after the dataset exists.
 * The README for the logging, logging-webapp, and demo examples have
    been updated accordingly.
 * This patch also includes some fixes needed to work on the CDH5.1
    QuickStart VM. I suspect more of the examples may have issues.
    So I'll file a follow-up JIRA to check them out and to update the
    top-level README to account for changes between the 4.4 and 5.1 VMs.
Not necessarily. If you installed with packages, that's fine. But if you installed with parcels and are using CM, you need the to put the plugins.d folder in /var/lib/flume-ng.

What I could do is create the symlink at the next level. i.e. /usr/lib/flume-ng/plugins.d/dataset-sink -> /var/lib/flume-ng/plugins.d/dataset-sink

This would be the easiest way to ensure things work both with and without CM.

Do you want me to do that? This script should only live between now and when 5.2 comes out.