Use NULL filter when the port format enumeration returns nothing.
Send clock update even when there is no clock.
Don't send data to a port when the node is not streaming
Add latency support to the clock update
Copy the unset_mask when copying the formats
Work on idle poll
Move node state to the node interface so that we can actually get it in
the sync case.
Add enabled field to the poll event
Work on audiotestsrc