[#202] store last id_vm in domain

lib/Ravada.pm

@@ -720,7 +720,7 @@ sub _upgrade_tables {
     $self->_upgrade_table('domains','spice_password','varchar(20) DEFAULT NULL');
     $self->_upgrade_table('domains','description','text DEFAULT NULL');
     $self->_upgrade_table('domains','run_timeout','int DEFAULT NULL');
-    $self->_upgrade_table('domains','id_vm',"int default NULL");
+    $self->_upgrade_table('domains','id_vm','int DEFAULT NULL');
 
     $self->_upgrade_table('vms','security','varchar(20) default NULL');
 }