Epics only models

rtcds: stopping and starting epics-only models will no longer try to start kernel modules or awgtpman. Also detects activation for these models based on rts-epics@.service rather than rts@.target

status output changed as appropriate for hosts without DAQ streaming and hosts without Dolphin.

Set env. variable

DAQ_STREAMING=true

and

IS_DOLPHIN_NODE=true

to have rtcds check status for daq streaming and dolphin modules respectively.