Merge "Use 1500 as MTU in NetDiagnostics if MTU is unknown" am: 2b7f9ee649 am: 526d247405 am: 0e8fa034e7

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/2618639

Change-Id: If4279c4dae3b5700aea8e5ea7f992b5fc088b673
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>