bpf: test.c - remove XDP program & add placeholder skfilter program am: 9ba9c1dbb4 am: eeceecab1f

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/3256439

Change-Id: Iba820aab0cfe7bb33b4cd4dd54b0a9ffc3642b7e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>