Revert "issue #91: modifying mplayerinstance logic to wait for mplayer process to exit before killing the process"

This reverts commit 1fa719391ce254809cbd9a67e2012be5f94ad98a.

this change is causing another issue when you start playback of a second
video.  the right solution may be to fix that issue, or do the blanking
another way.  regardless, for now reverting the original change.