btl/tcp: fix CID 710596

sizeof(addrs[0].addr_inet)==16 (so that it can handle IPv6 addresses),
but the memory that we are copying from (my_ss->sin_addr) is only 4
bytes long.  Don't copy beyond the end of that source buffer.

Signed-off-by: Jeff Squyres <jsquyres@cisco.com>

opal/mca/btl/tcp/btl_tcp_component.c

@@ -1184,7 +1184,7 @@ static int mca_btl_tcp_component_exchange(void)
                      (4 != mca_btl_tcp_component.tcp_disable_family)) {
                      memcpy(&addrs[current_addr].addr_inet,
                             &((struct sockaddr_in*)&my_ss)->sin_addr,
-                             sizeof(addrs[0].addr_inet));
+                            sizeof(struct in_addr));
                      addrs[current_addr].addr_port =
                          mca_btl_tcp_component.tcp_listen_port;
                      addrs[current_addr].addr_family = MCA_BTL_TCP_AF_INET;