[TIMOB-15193] Support backgroundColor=transparent on ListView (iOS7)

Fixes 
[TIMOB-15193](https://jira.appcelerator.org/browse/TIMOB-15193)
[TIMOB-15192](https://jira.appcelerator.org/browse/TIMOB-15192)

For regression test KS and make sure default behavior is unchanged for background color. See TIMOB-14392. Run on iOS6 and iOS7