Add a test for the interpreter

Just a basic test. If the interpreter is broken one of the tests
using it will break anyway ; the only important thing is to make
sure that it's actually running the tests and actually reporting
failures, if any. So here's a test doing that.

Test: atest FrameworksNetTests NetworkStackTests
Change-Id: I84ce651a6e3b64aa94daa5ee1fe014b27d2fba76