Default the roxie heartbeat on in containerized systems

This is on by default in bare-metal systems because of the default environment, but will be off for containerized systems.

Some cloud systems appear to enter a lower-power state after 5 minutes of inactivity.  If the first packet sent from server to worker is > MTU part of the message is lost, leading to a delay.  (See HPCC-28616 for an additional related fix.)