8bd00d5f7c
NetworkInterface throws Exceptions every time you look at it askance.
Try to make something we instantiate fully, once, and pass it around.
Partial MacAddress-ification as well, for good measure.
Test: as follows
- built
- flashed
- booted
- runtest frameworks-net passes
- basic IPv6 tethering works
Bug: 32163131
Bug: 62476366
Change-Id: I16c145fddb4e76387370338d792a438eed886d7f