Fix running 1.4/1.5 functional tests under MapReduce

A MapReduce job exists to run functional tests across a cluster. The job does not work out of the box, but requires some small code and, under some circumstances, configuration changes to start to work. This JIRA's purpose is to implement as many of those changes as possible, and document the rest.

This work only applies to the 1.4.x and 1.5.x lines. It does not include ACCUMULO-2005, which is related. It also does not block any releases since the tests can be run outside MapReduce.