Added unit test target, unit tests run and pass with bionic runner

As b/22772126 says, mm runtests should do the "right thing".
For clarity, this has been renamed so you use mm runtargettests.
The "right thing" is here interpreted to mean build & run the
unit tests using the bionic test runner on the target. All
tests should pass.

BUG: 22772126, 22874311
Change-Id: Id68bbf18bc7a8b3b36e80408af0399fdb53bad61
3 files changed