further bpf_existence_test code simplifications/clarifications am: e9e7741872

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

Change-Id: I1b9767f4c568695687eba482bd27002dc2d90c04
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>