NuPlayer: Fix seek stuck issue in video-only clips

Use mediaTime as maxMediaTime during 1st call to updateAnchor
in video-only case. This is required to handle a corner case
where the video frames given to mediaClock via addTimer call
were not drained after multiple seek operations.

In audio-video case, don't update maxMediaTime in video drain
path, let audio update the maxMediaTime in audio drain path.
Else, there will be frame drops for HFR case.

CRs-Fixed: 2602084
Change-Id: Iad4f4bfdfb32d0da196bfd218b73cef3db56df91