tests/examples/seek/seek.c: Don't go to READY on EOS as this avoids testing of seeking and restarting after EOS, use ...

Original commit message from CVS:
* tests/examples/seek/seek.c: (msg_segment_done), (main):
Don't go to READY on EOS as this avoids testing of seeking and
restarting after EOS, use the stop button when you want to READY.
Don't try to do a flushing seek in segment-done, it does not make
sense to use this for gapless playback and is not needed.