[VCN07.4] Add NOT_VCN_MANAGED for NetworkAgent implementations am: c8148a18d0

Original change: https://android-review.googlesource.com/c/platform/frameworks/opt/net/ethernet/+/1563133

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Ib3199fedff2d70a1a2245b9e5bea4c37424a1063