An example: let's say that there's an alsa sink and two filter sinks
on top of each other:
alsa-sink <- filter1 <- filter2
With the old code, if filter1 gets moved to another sink, and the
new sink doesn't have the LATENCY and DYNAMIC_LATENCY flags set
(unlike alsa-sink), filter1's flags are updated fine in the moving()
callback, but filter2 is not notified at all about the flag changes.
With this patch, the flag changes are propagated to filter2 too.