Set return message in close if a flush error is reported (which may be an error from a background flush). Ticket [97069ea11a]
Fix test failure socket-2.9: "1 {not owner}" instead of "1 {couldn't open socket address already in use}" by only setting returned error message if not jet set.
Add test cases for Bug [97069ea11a].
Centralize and clarify the user of 169.254.0.0 as a non-reachable address.
Revert the tests for bug#97069ea11a from socket.test, because it is hard to test with the socket command in a platform-independent way. As the bug is in tclIOChan.c and should be tested there with a dummy channel driver that can reliably reproduce the situation that suppresses the error message.
Fix for Bug [97069ea11a]: Set return message in close if a flush error is reported (which may be an error from a background flush)