Solution
As of VeriStand 2015 and CompactRIO 15.0 you are no longer required to compile a blank bitfile for cRIO-903x or cRIO-906x targets in order to use NI-986x series XNET modules.
If the system only contains NI-986x modules, then the controller should be set to
Scan Mode, as seen below:
Also, the 986x Support tab of the Port Settings should be left blank when configuring the XNET port.