Enables IPv6 fast fallback (Happier Eyeballs) for the connection. This behavior is similar to the Happy Eyeballs behavior described in RFC 6555 for improving connection times on networks where IPv6 is unreliable.
If both IPv6 and IPv4 addresses are resolved for a given host, WinHttp will begin by connecting to the first resolved IPv6 address with a short (300ms) timeout.
Should that connection fail, WinHttp will attempt to connect to the first resolved IPv4 address with the standard timeout.
Should the second connection fail, WinHttp will retry the first resolved IPv6 address with the standard timeout.
Should the third connection fail, WinHttp will revert to the default behavior for any remaining addresses, attempting a connection to each one with the standard timeout until a connection is made or no addresses remain.