My latest understanding of User Tracking and Nexus 5K series is that it is not supported due to a limitation of the MIB support in the NX-OS.
The current DCNM (release 5.2) is distinct from the LMS and Cisco Prime umbrella but that wil be changing a bit moving forwad as DCNM is enhanced and rolled into the Cisco Prime family. Last I heard there should be some information coming out of Cisco Live this week and a new release will have some additional functionality and better integration. Still, I doubt we'll see UT for the 5K due to the NX-OS limitation.
One way to do what you're asking apart from use of any of the Cisco products is to enable LLDP on your Nexus and servers. That will at least give you the ability to pull the information from the NX-OS command line ("show lldp neighbor")