Minor cleanups to NetdCallbackReceiver.onEvent.

- Clean up identical error messages.
- Fix the array length check for InterfaceAddressChange.

[Cherry-pick of 59be800e7fe81842aa8c77b91319f58ab165983d]

Bug: 9180552
Change-Id: Id871f481445b530c3ad749725f1548df0e3a1228