In this mode we accept previously set filter caps until
upstream renegotiates to something that is compatible
to the current filter caps.
This allows dynamic caps changes in the pipeline even
if there is a queue between any conversion element
and the capsfilter. Without this we would get not-negotiated
errors if timing is bad.
https://bugzilla.gnome.org/show_bug.cgi?id=739002
In the case the source has no caps, caps must be sent before segment. This
fixes few unit tests that where failing due to the new misordering warning.
https://bugzilla.gnome.org/show_bug.cgi?id=699968