[CRD iOS] Adding the PORTALLOCATOR_ENABLE_IPV6_ON_WIFI

Previously this flag is not set on the port allocator, which had probably
prevented Apple reviewers from connecting to our host. They are under
DNS64/NAT64 network so IPv4 address is not available at all.

This CL sets this flag so that WiFi connection can be established under
IPv6 network.

Bug: 800101
Change-Id: I36315f3daf3a71eb4a906719fc9230d8d70f6707
Reviewed-on: https://chromium-review.googlesource.com/854988
Reviewed-by: Lambros Lambrou <[email protected]>
Commit-Queue: Yuwei Huang <[email protected]>
Cr-Commit-Position: refs/heads/master@{#527834}
1 file changed