container.NetworkMounts(): don't lookup mounts twice

The code in question looks up mounts two times: first by using
HasMountFor(), and then directly by looking in container.MountPoints.
There is no need to do it twice.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

container/container_unix.go

@@ -65,12 +65,11 @@ func (container *Container) NetworkMounts() []Mount {
 		if _, err := os.Stat(container.ResolvConfPath); err != nil {
 			logrus.Warnf("ResolvConfPath set to %q, but can't stat this filename (err = %v); skipping", container.ResolvConfPath, err)
 		} else {
-			if !container.HasMountFor("/etc/resolv.conf") {
-				label.Relabel(container.ResolvConfPath, container.MountLabel, shared)
-			}
 			writable := !container.HostConfig.ReadonlyRootfs
 			if m, exists := container.MountPoints["/etc/resolv.conf"]; exists {
 				writable = m.RW
+			} else {
+				label.Relabel(container.ResolvConfPath, container.MountLabel, shared)
 			}
 			mounts = append(mounts, Mount{
 				Source:      container.ResolvConfPath,
@@ -84,12 +83,11 @@ func (container *Container) NetworkMounts() []Mount {
 		if _, err := os.Stat(container.HostnamePath); err != nil {
 			logrus.Warnf("HostnamePath set to %q, but can't stat this filename (err = %v); skipping", container.HostnamePath, err)
 		} else {
-			if !container.HasMountFor("/etc/hostname") {
-				label.Relabel(container.HostnamePath, container.MountLabel, shared)
-			}
 			writable := !container.HostConfig.ReadonlyRootfs
 			if m, exists := container.MountPoints["/etc/hostname"]; exists {
 				writable = m.RW
+			} else {
+				label.Relabel(container.HostnamePath, container.MountLabel, shared)
 			}
 			mounts = append(mounts, Mount{
 				Source:      container.HostnamePath,
@@ -103,12 +101,11 @@ func (container *Container) NetworkMounts() []Mount {
 		if _, err := os.Stat(container.HostsPath); err != nil {
 			logrus.Warnf("HostsPath set to %q, but can't stat this filename (err = %v); skipping", container.HostsPath, err)
 		} else {
-			if !container.HasMountFor("/etc/hosts") {
-				label.Relabel(container.HostsPath, container.MountLabel, shared)
-			}
 			writable := !container.HostConfig.ReadonlyRootfs
 			if m, exists := container.MountPoints["/etc/hosts"]; exists {
 				writable = m.RW
+			} else {
+				label.Relabel(container.HostsPath, container.MountLabel, shared)
 			}
 			mounts = append(mounts, Mount{
 				Source:      container.HostsPath,