mediav2 CTS: Match testSimpleDecodeQueueCSD to its NDK counterpart

testSimpleDecodeQueueCSD enqueues CSD before start as well as after
start. testSimpleDecodeQueueCSDNative queues CSD either before start or
after start. Further testSimpleDecodeQueueCSD forgets to rewind the
bytebuffer before queuing CSD. In effect the test is not queueing CSD
twice, but only once. This is corrected and its behavior is made
identical to its NDK counterpart.

Bug: 186182806
Test: atest android.mediav2.cts.CodecDecoderTest

Change-Id: I8a8a1f004b51ea5221d878c58a264596fc4693b2