DataItem::access() being recursive causes problems

[joachim-n]

DataItem::access() recurses down into complex properties, so calling access() on root calls it on everything.

This causes problems with certain structures and default values, particularly with single-valued complex data. Consider the following property structure:

- root
  - scalar_default
  - complex_single
    - child_scalar_default

When the data is first instantiated, nothing is set.

Calling access() causes the following

• scalar_default is instantiated and have its default set, which is OK.
• complex_single is instantiated, which is ok, so far...
• but then we recurse, because it's single-valued
• child_scalar_default is instantiated, and gets its default set.

This is not OK, because we now have this data:

- root
  - scalar_default: foo
  - complex_single
    - child_scalar_default: foo

The user has not set the optional complex_single, but it now exists with a value set!

This situation exists in DCB:

• README is a scalar with a default
• Admin settings form is a complex single with properties with default values

Currently, calling access() on the DCB data root will cause the module to have an admin settings form by default, which is not intended.