MediaSlider was broken occasionally during rebuffering

MediaSlider was broken occasionally during rebuffering

[Title] MediaSlider was broken occasionally during rebuffering
[Problem] MediaSlider was broken when seeking and resume in MediaPlayer
[Cause] TimeRanges are buffering ranges in gstreamer and it represented start point and end point of buffering. Normally TimeRagnes length is one, but some times TimeRanges is bigger than 1.
And that time, there exists difference between first and second timeRanges.
[Solution] If there exists difference between first end value of timeRange and second start value of timeRange, second start value is set to first end value.

Change-Id: I545cbec95faaae319c52b481e5256dc9e3acfbdd