Add NET_CAPABILITY_NOT_VCN_MANAGED to ConstantsShim.

This is new in S.

The Merged-In tag in this CL is from aosp/1605016, which is an
arbitrary CL that is already in sc-dev, with the purpose of
preventing this CL from reaching sc-dev.

Bug: 167645754
Ignore-AOSP-First: need to fix build
Test: m NetworkStack CtsNetTestCasesLatestSdk CtsHostsideNetworkTests CtsHostsideNetworkTestsApp
Change-Id: I941024a1661a66794e97e8f2b0e992f83f673bf4
Merged-In: I2ec0aa737804cc3ea5fce9326f84c1e4b5e4972c