Test failures

[NyCodeGHG]

While trying to add support for API 23 to maestro, I noticed some test failures:

Especially the tcp forwarding tests, I suspect that there might be a bug in there which prevents maestro's grpc server to work on 23, but i could be wrong.

Also my cpu usage goes up a lot after running the tests and only goes down after a restart.

[sleekweasel]

You probably had more than one emulator or device attached at a time, or your emulator wasn't called emulator-5554, or perhaps no adb available:

• I get the same basic failures (but different stack traces)
  ** with two emulators, or
  ** with one emulator called emulator-5556, or
  ** if adb is mysteriously absent
• With one emulator called emulator-5554, I have passes and the root/unroot skips.

It would be nice if there were an environment variable to make Dadb a bit more noisy about what devices it can see.

With my multiple devices pull request - #80 - it's happy if there are multiple devices, so long as emulator-5554 is around.