kmswebrtcendpoint: fix get_video_recv_info
kmswebrtcendpoint: fix get_video_recv_info

It must return FALSE if data has not been taken.

Change-Id: I63f5816b8a69732430ab3dd2084be4c8254ad15d

Kurento/kms-elements,Kurento/kms-elements,Kurento/kms-elements