ssh: change the local copy of the ServerConfig passed to NewServerConn

Otherwise callers are forced to serialize access to the ServerConfig.

Change-Id: Id36f4d2877ea28b18447ef777d3839b21136c22f
Reviewed-on: https://go-review.googlesource.com/42821
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

ssh/server.go

@@ -147,12 +147,12 @@ type ServerConn struct {
 // Request and NewChannel channels must be serviced, or the connection
 // will hang.
 func NewServerConn(c net.Conn, config *ServerConfig) (*ServerConn, <-chan NewChannel, <-chan *Request, error) {
-	if config.MaxAuthTries == 0 {
-		config.MaxAuthTries = 6
-	}
-
 	fullConf := *config
 	fullConf.SetDefaults()
+	if fullConf.MaxAuthTries == 0 {
+		fullConf.MaxAuthTries = 6
+	}
+
 	s := &connection{
 		sshConn: sshConn{conn: c},
 	}