BUG/MINOR: proto_reverse_connect: fix FD leak upon connect

BUG/MINOR: proto_reverse_connect: fix FD leak upon connect

new_reverse_conn() is creating its own socket with
sock_create_server_socket(). However the connect is done with
conn->ctrl->connect() which is tcp_connect_server().

tcp_connect_server() is also creating its own socket and sets it in the
struct conn, left the previous socket unclosed and leaking at each
attempt.

This patch fixes the issue by letting tcp_connect_server() handling the
socket part, and removes it in new_reverse_conn().