vp8dec: Reset output and input states when changing format
vp8dec: Reset output and input states when changing format

https://bugzilla.gnome.org/show_bug.cgi?id=734266

ndufresne/gst-plugins-good,jpakkane/gstreamer-plugins-good,ndufresne/gst-plugins-good,wkatsak/gst-plugins-good,surround-io/gst-plugins-good,surround-io/gst-plugins-good,vatavuserban/gst-plugins-good,wkatsak/gst-plugins-good,vatavuserban/gst-plugins-good,wkatsak/gst-plugins-good,surround-io/gst-plugins-good,jpakkane/gstreamer-plugins-good,ndufresne/gst-plugins-good,jpakkane/gstreamer-plugins-good,ndufresne/gst-plugins-good,vatavuserban/gst-plugins-good,jpakkane/gstreamer-plugins-good,vatavuserban/gst-plugins-good,wkatsak/gst-plugins-good,surround-io/gst-plugins-good