When the value of enyo.Input changes, only call setAttribute() if we don...

...’t have a node yet; if we do have a node, set its value property instead.

This fixes a strange bug where a change event would not be fired as expected if a) the node was rendered; then b) the value of the input was set programatically; then c) the user cleared the contents of the field and pressed Enter or caused the input to be blurred.

Enyo-DCO-1.1-Signed-Off-By: Gray Norton (gray.norton@lge.com)