move data grid list item type props to local variable
move data grid list item type props to local variable

utils.clone() was producing a shallow copy causing issues when
switching between item types. Moving to a local variable removes the
need for the clone.

Issue: ENYO-1181
Enyo-DCO-1.1-Signed-off-by: Ryan Duffy (ryan.duffy@lge.com)

enyojs/enyo-strawman