unusual error code returned when checking configured submodules for non-existing submodule

When a service checks if a submodule is configured in requested api/slot/subslot combination, it may return unusual errorcodes like "ERR_PNS_IF_MODULE" or "ERR_PNS_IF_SUBMODULE" indicating error in ModuleIdentNumer or SubmoduleIdentNumber. That is missleading. A deeper analysis showed that the textual description of the error code does not match its usage in protocol stack. Thus, this issue is fixed by modifying the textual explanation of the error code. Neither the errorcode define nor its number will be changed, only the text in explanation of the errorcode itself.