Fix location query under some circumstances.

- Yahoo returns a single JSON object instead of an array in case there's
  only one match; adjust for that.
- A postal code is not guaranteed to be returned.
- Fix determination whether postal code needs to be shown: It needs to
  be shown when there's any duplicate name/country pair, not only if
  there's a duplicate to the first entry.

Change-Id: I132de203cca72ec9e78ded53837540bbd0044788