Don't use short update interval when using JsApiReporter

Newest HTMLUnit removed the rhino globals we were using to detect if we were
running under HTMLUnit so things reverted to slow runnning. This will make it
use a long updateInterval when running with the JsApiReporter which should
only be when running the test goal.
Merge pull request #160 from dtabuenc/master

Re-fix exponential slowness when running under maven.