direct-tcpip driven gateways didn't actually use the gateway

[bitprophet]

Due to an incredibly boneheaded mistake, the gateway connection used the gateway info as the host key but still made a connection to the real target and cached that instead.

So the gatewaying behavior worked -- two cached connections were involved with one passed in as the socket and so on -- but the end result was gatewaying to the target via itself, not via the configured gateway.

This issue description is already about 10x longer than the fix.