Deallocate port before trying to delete iptables chain

Fixes #7954
Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com>

daemon/networkdriver/portmapper/mapper.go

@@ -4,11 +4,11 @@ import (
 	"errors"
 	"fmt"
 	"net"
-	"strings"
 	"sync"
 
 	"github.com/docker/docker/daemon/networkdriver/portallocator"
 	"github.com/docker/docker/pkg/iptables"
+	"github.com/docker/docker/pkg/log"
 )
 
 type mapping struct {
@@ -127,10 +127,7 @@ func Unmap(host net.Addr) error {
 	containerIP, containerPort := getIPAndPort(data.container)
 	hostIP, hostPort := getIPAndPort(data.host)
 	if err := forward(iptables.Delete, data.proto, hostIP, hostPort, containerIP.String(), containerPort); err != nil {
-		// skip "no chain" errors because we can safely release port in this case
-		if !strings.Contains(err.Error(), "No chain/target/match by that name") {
-			return err
-		}
+		log.Errorf("Error on iptables delete: %s", err)
 	}
 
 	switch a := host.(type) {
@@ -139,7 +136,6 @@ func Unmap(host net.Addr) error {
 	case *net.UDPAddr:
 		return portallocator.ReleasePort(a.IP, "udp", a.Port)
 	}
-
 	return nil
 }