Figure out what to do about Tomcat 6 End of Life

Tomcat 6 will be end of life on Dec 31 2016.

Even though that's a quite a while from now, it's best to stay ahead of things, so it would be good if we looked into a plan for this.

Here are some options:

1. Upgrade to Tomcat 7
2. Upgrade to Tomcat 8
3. Switch to embedded Jetty 9

I imagine upgrading to Tomcat 7/8 would be the easiest solution. I haven't looked into it much, but I imagine the build and deploy process could remain relatively the same; though we'd probably have to tweak some config files and things. As for which version, Tomcat has this page to help.

Switching to embedded Jetty 9 would require changing the build and deploy process, though that might be a good thing given how that can be complicated/confusing for users. And I know Tomcat makes things difficult for our packaging team in Cloudera. Many other Hadoop projects use embedded Jetty as well. We do know that Oozie runs properly in Jetty because our unit tests use Jetty.

As part of this JIRA, the assignee should probably look into more specific pros/cons of the options and we should all reach a consensus before moving forward.