Fix certain setting writes being incorrectly skipped.

If a value that previously had a very long value (over the 500 char
threshold) is now set to null, isRedundantSetValue would incorrectly
return true even though the value was changed.

Change-Id: Ia5304743024ec01024be98aa51ed260d38caf93c
Merge "Fix certain setting writes being incorrectly skipped." into cm-10.2