Pass Correct Node List Key

[danehans]

node list is pulling the incorrect value from the json response. Call the correct key from the map. If a descr is not provided in the json response, then drop the descr.

$ acictl node list
NAME		DESCRIPTION
apic1		%!s(<nil>)
Leaf-101	%!s(<nil>)
Spine-201	%!s(<nil>)