This patch changes `tcp_ctloutput_[gs]et()` such they expect the `inp` to be write locked. This is a preparation to allow to call `tcp_ctloutput_set()` from contexts other than `setsockopt()`. Support for this will come in a follow-up commit.
While there, change the function signatures to pass only the `inp` around and have this as the first parameter as suggested by glebius@ to simplify future work.