further bpf_existence_test code simplifications/clarifications am: e9e7741872

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/2156256

Change-Id: Ibdd303eaeca7fc61e9abd2a3277bd5efc99343fd
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>