We now (well, after a few days of experimentation) see that you must issue a “Detach Network ISO USB Device” command to un-busy the Lifecycle Controller and allow the IDRAC job to complete. We can now: Sure would have been nice if the document "Dell™ Lifecycle Controller 2 Web Services Interface Guide for Windows" had the slightest hint that this was necessary (see sections 11.3.6 and 11.3.7). I just can't wait to stumble over more things that are missing. Oh well, I guess that's what these forums are for. 
I'm trying to use various remote calls to an R720 IDRAC. I'm using various wsman calls from "Dell™ Lifecycle Controller 2 Web Services Interface Guide for Windows". I can successfully interrogate and change boot settings (e.g., using "CALL winrm e cimv2/root/dcim/DCIM_BootSourceSetting") by making an IDRAC job (.../DCIM_BIOSService. . .) and initiating a reboot. I normally see the job status go from Ready to Scheduled to Running, and the job blasts into any default boot that the server was thinking it was going to do from the current state of boot entries. But, I now notice that if I boot the server using an iso boot (BootToNetworkIso Lifecycle winrm call), and then issue the IDRAC job,  it gets stuck in Ready. My previous successful job completion was when the server was idle after booting into WinPE from the internal SD card. At this point, we have to power cycle the IDRAC to do anything else. Is there any reason that the boot source or method (iso boot vs. discovered boot entry) should make a difference?  Thanks.
Problem completing IDRAC jobs using Lifecycle Controller Web Services to an R720