Fix seeking to end using seek bar (#6763)

Merging #6074 has caused a new edge case for VBR audio files, in which
using the seek bar to seek to the end of an episode sometimes hits the
new code path, and the `skip()` function is called.

Because `skip()` invokes `endPlayback()` with `hasEnded` set to `false`,
post-processing tasks are not executed unless the pre-seek position
falls within the "Smart mark as played" range. If "Smart mark as played"
is set to `Disabled`, or the pre-seek position is outside that range,
then the episode is not marked as played, and not removed from queue.

This commit fixes that edge case by replacing `skip()` with a direct
call to `endPlayback()`, with `hasEnded` set to `true`.

core/src/main/java/de/danoeh/antennapod/core/service/playback/LocalPSMP.java

@@ -345,7 +345,7 @@ public class LocalPSMP extends PlaybackServiceMediaPlayer {
 
         if (t >= getDuration()) {
             Log.d(TAG, "Seek reached end of file, skipping to next episode");
-            skip();
+            endPlayback(true, true, true, true);
             return;
         }