It may come from nfs-utils-1.3.0-0.21.el7_2.1.x86_64 ??
I have reproduce it right now by installing nethserver-backup module on a NethServer bound to a remote LDAP.
The user was listed after a reboot.
The nfsnobody user is retrieved from the local accounts, not from the remote ldap.
Do you need the list of installed packages?