Add test to verify socket close when firewall is enabled am: 9b659bb6c3 am: caed9a8b85

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

Change-Id: Iac4c9423b92027fb774cd1bbf9c29afbc3be6e04
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>