commit 8ea45483fc59ef63851a64640ed1bb18c09f7ea9
author Erik Kline <ek@google.com> Mon Feb 13 17:28:53 2017 +0900
committer Erik Kline <ek@google.com> Tue Feb 14 12:20:39 2017 +0900
tree 86307cb74e2023e56019eb0f8b9a219633be6e15
parent fb19d8d7c142aae0aaa9782db145fee072071fbf

Cleanup in the face of upstream error

If either enableNat() or startInterfaceForwarding() fail, be sure
to cleanup any commands that might have succeeded.

Most of this change is a refactoring of cleanupUpstreamIface() into
two methods, one of which (cleanupUpstreamInterface()) is reused
in error handling scenarios.

Test: as follows
    - built (bullhead)
    - flashed
    - booted
    - runtest -x .../tethering/TetherInterfaceStateMachineTest.java passes
Bug: 32031803
Bug: 32163131

Change-Id: Ia4d56e03beeab1908d8b8c2202e94992f1aa58a4