Fix Auto-Resume

[leggettc18]

The code that resumes played episodes from their last-played position is currently broken as of commit 7d2520e on native-player. Likely a broken calculation as GStreamer works in nanoseconds while Clutter doesn't.

[leggettc18]

This appears to be fixed as of 7a8b7d4

It was frustrating because there's a weird delay that happens between when the episode uri is set (at which point playback can commence right away) and when seeking can occur. I'm not sure why this is, but adding a short timeout that attempts to seek until the seek succeeds works for now.