Add ICMP header length constant am: 64a0446d9f am: 720e1b2a5a

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/libs/net/+/22964660

Change-Id: Id39800acafaf750bfb5e85993bceb646f20b9f85
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>