Merge "Add additional javadoc for VcnManager" am: ba3f1179a8 am: e1a23d3245 am: 3e867f4ff7

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1458805

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I37106e194123c0bab6cb187f194bc7f3b619b693