[#525] v2/container: Return session token in GetExtendedACL

In recent API changes `GetExtendedACLResponseBody` carries session token.
In recent API Go lib changes `eacl.Table` structure carries related session
token.

Write session token of eACL table from sidechain to GetExtendedACL response
body in node's `ContainerService` server.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/services/container/morph/executor.go

@@ -110,6 +110,7 @@ func (s *morphExecutor) GetExtendedACL(ctx context.Context, body *container.GetE
 	res := new(container.GetExtendedACLResponseBody)
 	res.SetEACL(table.ToV2())
 	res.SetSignature(signature.ToV2())
+	res.SetSessionToken(table.SessionToken().ToV2())
 
 	return res, nil
 }