adapter: fix to get valid (buffer_)list
adapter: fix to get valid (buffer_)list

get_list/get_buffer_list should be done with buffers in adapter remaining
while take_list/take_buffer_list flushes each buffer one by one.

https://bugzilla.gnome.org/show_bug.cgi?id=752116

krichter722/gstreamer,krichter722/gstreamer,centricular/gstreamer,jpxiong/gstreamer,StreamUtils/gstreamer,krichter722/gstreamer,jpxiong/gstreamer,jpxiong/gstreamer,centricular/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,krichter722/gstreamer,jpxiong/gstreamer,centricular/gstreamer,krichter722/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,centricular/gstreamer,centricular/gstreamer,jpxiong/gstreamer