Refactor existing test: add an extra assertion and use sinon's firstCall, secondCall spy properties
Add a test to ensure that a failed deferred seek - where we wait until the device finishes buffering before calling JumpForward/JumpBackward, but the device returns an error code from the call  - returns us to the PLAYING state (test already satisfied by existing code).
Call Samsung Resume() function after the Jump API call, to avoid a single frame being played at the old position before the jump occurs.
Add a comment to explain why we ignore attempts to seek near the current time, despite the fact that we also cater for JumpForward() and JumpBackward() returning a failure code.