CID 330954: Possible Control flow issues in lib/isc/netmgr/tlsstream.c

Coverity Scan identified the following issue on main:

*** CID 330954:  Possible Control flow issues  (DEADCODE)
/lib/isc/netmgr/tlsstream.c: 423 in tls_do_bio()
417     		return;
418     	}
419     
420     	switch (tls_status) {
421     	case SSL_ERROR_NONE:
422     	case SSL_ERROR_ZERO_RETURN:
>>>     CID 330954:  Possible Control flow issues  (DEADCODE)
>>>     Execution cannot reach the expression "received_shutdown" inside this statement: "if (sent_shutdown && receiv...".
423     		if (sent_shutdown && received_shutdown) {
424     			/* clean shutdown */
425     			isc_nm_cancelread(sock->outerhandle);
426     			isc__nm_tls_close(sock);
427     		};
428     		return;

This likely appeared with 11ed7aac.