can_dump_inet_sk(): fix error message

In other similar cases we print option as it appears on the command
line, i.e. --option, but not here. Fix it to make it more clear.

Was:
	Error (sk-inet.c:141): Connected TCP socket, consider using tcp-established option.

Now:
	Error (sk-inet.c:141): Connected TCP socket, consider using --tcp-established option.

Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>