Set location of download buffer / revert old buffer

As per:
https://github.com/rubenrua/GstreamerCodeSnippets/blob/master/0.10/Python/pygst-sdk-tutorials/playback-tutorial-4.py

"self.player.props.flags |= (1 << 7)" doesn't actually do anything unless you set a cache location. Should make for smoother playback/less dropouts in the middle of song.