Show "0 B used" when no data usage this cycle

When the latest cycle has no data usage, currently it shows all time
usage without cycle info, which could confuse user.

Change to "0 B used used xxx - xxx" to fix this issue.

Fix: 292346951
Test: manual - on Mobile Settings
Test: unit tests
Change-Id: Ic06fd63a3bc049d70538d0a3cd1fa3d62dbd71d7