Add a ModulePdoGroup if none is described in the Slave Type and Slots nodes.

The case is as follows:

In Esi for Device there is no description for ModulePdoGroup in Type and Slots nodes but the Module description has ModulePdoGroup = 0. It is assumed that the default value is 0 when there is no description in the device, but the current implementation in the DTM assumes the value is -1.