Fix a bug in free_encoder()
Fix a bug in free_encoder()

Move vpx_free(buffer_pool) after vp9_remove_compressor()

buffer_pool needs to be free after cpi because buffer_pool
contains allocated buffers that will be free in
vp9_remove_compressor()

Change-Id: I8bcedae2858cfe132bde110c8f3f6b55dcbe3f36

ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx