tests/acceptance/migration: Default to -nodefaults

We don't need the default options to run this test.

This fixes errors when running a binary built with
--without-default-devices such:

  ERROR: qemu-system-arm: Unsupported NIC model: virtio-net-pci

Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Wainer dos Santos Moschetta <wainersm@redhat.com>
Message-Id: <20200129212345.20547-28-philmd@redhat.com>
[PMD: Rebased]
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

tests/acceptance/migration.py

@@ -41,11 +41,13 @@ def assert_migration(self, src_vm, dst_vm):
         self.assertEqual(src_vm.command('query-status')['status'],'postmigrate')
 
     def do_migrate(self, dest_uri, src_uri=None):
-        source_vm = self.get_vm()
         dest_vm = self.get_vm('-incoming', dest_uri)
+        dest_vm.add_args('-nodefaults')
         dest_vm.launch()
         if src_uri is None:
             src_uri = dest_uri
+        source_vm = self.get_vm()
+        source_vm.add_args('-nodefaults')
         source_vm.launch()
         source_vm.qmp('migrate', uri=src_uri)
         self.assert_migration(source_vm, dest_vm)