Commit 786f37ae accidentally changed seeking behavior such that
continuous seeking (holding the seek button down) would use the previous
seek target timestamp, instead of the new video timestamp. (This is for
the default mode, seeking to keyframes.)
The result is that the movement on the seekbar is smooth, but the way
the video updates is awkward. Some might actually prefer the new
behavior (and some players effectively show similar bahavior), but I
don't. So restore the old behavior.
This is done in two steps:
First: strictly wait for the entire seek process to finish, which will
effectively make the seeking code pick up the new video timestamp
correctly.
This would play audio immediately, which would result in noise during
continuous seeking, which leads to second: explicitly abort the playback
restarting process if this case is detected, and never play audio.
af0a8d7478