TetherOffload: Address VTS failure in AdditionalStopsWithInitReturnFalse

- Currently if NAT iface is not added, IPACM cache setupstream
  events but default gw index will be set only after adding
  NAT iface. If IPACM receives stopOffload in between, then
  it is returning input check error to framework. Add check and
  clear event cache in case of stopOffload.

- Fixed variable shadowing issue in HAL.

Test: - build and boot - pass
      - VtsHalTetheroffloadControlV1_0TargetTest    - pass
      - VTS Test AdditionalStopsWithInitReturnFalse - pass

Change-Id: I335b7834c9a7567bc5bc05f683ec789b39c1efac
Crs-fixed: 2228293
bug: 77996655
(cherry picked from commit b8c3d7ae84541f40c7b82e6c32ea1915ad4b1766)
2 files changed
tree: 6abe6701a25898b173e9685ce6fe624e37b87514
  1. msm8998/
  2. Android.mk