Fix issue that timeline goes back to 00:00 during pressing FF button repeatly
Fix issue that timeline goes back to 00:00 during pressing FF button repeatly

[Title] Fix issue that timeline goes back to 00:00 during pressing FF button repeatly
[Problem] N_SE-38067
[Cause] playbackPosition() method return 0.0f when error occured
[Solution] Set m_cachedTime value when return value of currentTime method is not 0.0f caused by internal gstreamer error

Change-Id: Ia831ec1645a075c17c1d0450b395e7791edab805

youfoh/webkit-efl,youfoh/webkit-efl,youfoh/webkit-efl,youfoh/webkit-efl,youfoh/webkit-efl,youfoh/webkit-efl,youfoh/webkit-efl,youfoh/webkit-efl,youfoh/webkit-efl,youfoh/webkit-efl,youfoh/webkit-efl