Support subnet host-routes by adding InterfaceRouteTable to the ports

In this logic, i first assume that the tuple (ipaddr, prefixes) is also present in the new_host_prefixes.
If the length of two lists doesn't match, it means that my assumption is false and i set the variable 'already_exists' to False.
If the length matches, i then iterate through the list to see if the prefixes are same.