tee: Set GST_PAD_FLAG_PROXY_CAPS before forwarding sticky events
tee: Set GST_PAD_FLAG_PROXY_CAPS before forwarding sticky events

https://bugzilla.gnome.org/show_bug.cgi?id=752213

StreamUtils/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer