When downstream has any caps, vaapi should not shovel vaapi featured
buffers, but rather plain raw video, assuming always the worst case
scenario (downstream cannot handle featured video memory but raw
system memory buffers).

This patch query the peer caps without any filter, to know if
donwstream just ask for any caps, if so jump to the color space
checking, otherwise do the caps intersection and continue with the
feature selection algorithm.

Fixes: #139