Add test to verify socket close when firewall is enabled am: 9b659bb6c3

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/23206439

Change-Id: I4c61103f035609fb55c800a55533dcf39fab8da6
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>