T7252: Allow vpptun and vpptap for constraint validator

It fixes cases whey we want to use VPP kernel interfaces for OSPF
But VPP kernel interface is not exists on this step

set vpp interfaces loopback lo0 kernel-interface 'vpptun0'
set protocols ospf interface vpptun0 area '0'

Incorrect path /sys/class/net/vpptun0: no such file or directory