DDS — Behavior on creation failure

Ref-21 Error_status_on_create_calls

The specification does not explain the return value of the factory
"create" calls if the operation fails, for example due to inconsistent
QoS.

**PROPOSAL**

Add text that explains that in case of failure the return value is NIL
(as defined on each PSM).

This affects 2.1.2.2.2.1, 2.1.2.2.1.1, 2.1.2.2.1.5, 2.1.2.2.1.7,
2.1.2.2.1.9, 2.1.2.4.1.5, 2.1.2.5.2.5

see below