Fake InterVpnLink VpnInterfaces not removed when InterVpnLink is removed

InterVpnLink logic "installs" some fake VpnInterfaces on given DPNs so that VpnManager and FibManager maintains LFIB and FIB tables in DPNs where the implied L3VPNs may not have Footprint on it.
It aims to also ensure that the LFIB and FIB is still maintained in DPNs where the last real VpnInterface has been removed.

However, when the InterVpnLink is removed, the fake VpnInterface is not removed on cascade