ENYO-3250: fix file-URL xhr code for webOS 3

enyo.xhr.request was running file URLs through simplification logic
that triggered a weird behavior on webOS 3 -- window.location.host isn't
set to "" like on other file-protocol using setups, but instead
maps to a app-specific string. Unfortunately, the URL lookup didn't
actually allow using that host name to load files.

Enyo-DCO-1.1-Signed-Off-By: Ben Combee (ben.combee@lge.com)
Merge pull request #538 from enyojs/ENYO-3520-unwiredben

ENYO-3250: fix file-URL xhr code for webOS 3