WIP: better precondition checks for harness (checks often fail due to some kind of race)
fixup! WIP: better precondition checks for harness (checks often fail due to some kind of race)
fixup! fixup! WIP: better precondition checks for harness (checks often fail due to some kind of race)

Check that b2g process has stopped before returning from .stop()
fixup! fixup! fixup! WIP: better precondition checks for harness (checks often fail due to some kind of race)
Merge pull request #205 from mozilla-b2g/jgraham/preconditions_2

Better precondition checks for harness