This defaults the channel to stalled and forces the system to take action to mark it as not stalled.  In a bad state we want to default to bad, not a bad state hidden because the producer wasn't run.

This adds code to the shmem receiver to have it signal when it has taken 2s to look for new data.

This is meant to be a simple flag to show when the producer is 'stuck' waiting for data.

This fits better with recent packaging changes and auto configuration of the device files.

* Increases the DAQ_TRANSIT_MAX_DCU to 256
* Updates the tests of daqd/nds to run with more dcus and sample more channels
* Fixes a spurious failure in the edcu test to keep tests passing

The test is to:

* start a simulated IFO (via fe_multi_stream_test)
* start daqd
* read live data from nds
* verify the data

This updates the NDS2 client detection, reimplements fe_stream_check_nds,
and adds some test harness logic.