Bug 1067482 - Add treeherder support for Android instrumentation tests

I think this is all that's needed, but I haven't seen the changes take effect in my Vagrant instance.

If it's working, http://192.168.33.10/ui/#/jobs?repo=ash should have a group labeled "Inst" with both "Ba" and "Br" tests contained within it on the Android 4.0 line.
This section is a mapping of job name to group (the key is the job name, the value the group). As such, we need two lines added here rather than one, one for "Android Instrumentation Background" and one for "Android Instrumentation Browser" to put both of them in the "
+ "Android Instrumentation Tests": "Android Instrumentation Tests" group.