[VCN07.3] Add NOT_VCN_MANAGED for NetworkAgent implementations am: 336013c3dc am: b200743939

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Wifi/+/1563135

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I79887cbe20347ee940fd076403e62063928acf2e