[rbp/omxplayer] Handle displaytime more like dvdplayer

We had various glitches when mixing seeking and trickplay with online streams or dvd content.
This tries to match more closely what dvdplayer does and fixes some seek/trickplay jumping issues
Merge pull request #3108 from popcornmix/dvddisplaytime

[rbp/omxplayer] Handle displaytime more like dvdplayer