libcontainer/console_linux.go: Make SaneTerminal public

And use it only in local tooling that is forwarding the pseudoterminal
master.  That way runC no longer has an opinion on the onlcr setting
for folks who are creating a terminal and detaching.  They'll use
--console-socket and can setup the pseudoterminal however they like
without runC having an opinion.  With this commit, the only cases
where runC still has applies SaneTerminal is when *it* is the process
consuming the master descriptor.

Signed-off-by: W. Trevor King <wking@tremily.us>

tty.go

@@ -74,6 +74,9 @@ func (t *tty) recvtty(process *libcontainer.Process, socket *os.File) error {
 	if err != nil {
 		return err
 	}
+	if err = libcontainer.SaneTerminal(f); err != nil {
+		return err
+	}
 	console := libcontainer.ConsoleFromFile(f)
 	go io.Copy(console, os.Stdin)
 	t.wg.Add(1)