Merge "Add test for Vpn#prepare()" into sc-dev am: f89a629776 am: 66737a8c5d

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/15606164

Change-Id: Icec2f3508932abd460b2605881b54c5d0cfafb35