core: Move sending of final boundary to gdata_upload_stream_close()
core: Move sending of final boundary to gdata_upload_stream_close()

It makes more sense for the final boundary to be sent to the server when
the stream is closed, and makes the bookkeeping simpler. It also means that
the boundary can't be sent multiple times, which was possible before if
g_output_stream_write() was called multiple times after EOF.

Distrotech/libgdata,Pecisk/libgdata,Pecisk/libgdata,pwithnall/libgdata,Distrotech/libgdata,Pecisk/libgdata-gtasks,Pecisk/libgdata,pwithnall/libgdata,Pecisk/libgdata-gtasks,GNOME/libgdata,Pecisk/libgdata-gtasks,Distrotech/libgdata