Adventureworks policies deny vNet peering not working cause of wrong policy mode

[marenskoetter]

Description:
Both policies "Deny vNet peering" and "Deny vNet peering cross subscription" are not working because of policy mode need to be "all" instead of "indexed". Reason for this it that Microsoft.Network/virtualNetworks/virtualNetworkPeerings does not have location or tag property. Therefore indexed can't be used.

Steps to reproduce

1. Policy, as it is today, does not work when assigned at management group, peering can still be created
2. Edit the defintion to Policy Mode "all"
3. Now the policy works as expected and peering creation is blocked