Command returns 0.0.0.0 for IP but only for leader
I ended up using {{.ManagerStatus.Addr}} and stripping the port number from the results with sed.  

for NODE in $(docker  node ls -f 'role=manager' --format '{{.Hostname}}'); do
  docker node inspect --format '{{.ManagerStatus.Addr}}' ${NODE} | sed 's/:2377//'
done