MINOR: tcp: add "tcp-request connection expect-netscaler-cip layer4"

MINOR: tcp: add "tcp-request connection expect-netscaler-cip layer4"

This configures the client-facing connection to receive a NetScaler
Client IP insertion protocol header before any byte is read from the
socket. This is equivalent to having the "accept-netscaler-cip" keyword
on the "bind" line, except that using the TCP rule allows the PROXY
protocol to be accepted only for certain IP address ranges using an ACL.
This is convenient when multiple layers of load balancers are passed
through by traffic coming from public hosts.