Allow using runtest with frameworks-services tests

( cherry-pick of 00d6fa79f7e384d3dde90118e08fcf7f7d5dc606 )

Specifying a runner allows developers to run commands like:

`runtest frameworks-services`

without getting a message like:

"Could not find instrumentation
com.android.frameworks.servicestests/android.test.InstrumentationTestRunner
on device."

Bug: 28833951
Change-Id: I76fb58a8fa16db503c8e98eb5a09c481d41e0a76
Test: Described above
1 file changed