Enable ntuple filters for IPv6

[cjdoucette]

We have found that even though a NIC may report that it supports ntuple filters, either the NIC or the driver may not support matching IPv6 addresses in practice. Therefore, ntuple filters are currently disabled for IPv6 in Gatekeeper.

When we find that support for IPv6 ntuple filters are stable enough (possibly with a DPDK update), we should enable their use in Gatekeeper.

[cjdoucette]

The Intel 82599 datasheet says that IPv6 addresses in ntuple filters are simply not supported, so we may need to wait for hardware to support this feature:

Download link:

https://www.intel.com/content/dam/www/public/us/en/documents/datasheets/82599-10-gbe-controller-datasheet.pdf