para_play: Avoid invalid time display on pause.

para_play: Avoid invalid time display on pause.

When para_play enters pause mode, playback is stopped by notifying
the writer node, causing it to terminate in the next iteration of the
main loop. Until then the play time is computed incorrectly because
we add the running time of the moribund writer node to the start time
computed from the *new* start chunk set in com_pause().

Fortunately, the fix is simple. We just need to enqueue a reposition
request in the same way the ff and jmp commands do.