caddyhttp: Fix HTTP->HTTPS redir not preferring HTTPS port if ambiguo…

…us (#4530)

modules/caddyhttp/autohttps.go

@@ -232,7 +232,7 @@ func (app *App) automaticHTTPSPhase1(ctx caddy.Context, repl *caddy.Replacer) er
 				// port, we'll have to choose one, so prefer the HTTPS port
 				if _, ok := redirDomains[d]; !ok ||
 					addr.StartPort == uint(app.httpsPort()) {
-					redirDomains[d] = append(redirDomains[d], addr)
+					redirDomains[d] = []caddy.NetworkAddress{addr}
 				}
 			}
 		}