Fix primary-path-ref

[italobusi]

OLD

    |  |  |        |     +-- primary-path-ref* []
    |  |  |        |        +-- (primary-path-exist)?
    |  |  |        |           +--:(path-ref)
    |  |  |        |           |  +-- primary-path-ref    leafref
    |  |  |        |           +--:(path-request-ref)
    |  |  |        |              +-- path-request-ref    leafref

NEW

    |  |  |        |     +-- primary-path* []
    |  |  |        |        +-- (primary-path-exist)
    |  |  |        |           +--:(path-ref)
    |  |  |        |           |  +-- path-ref    leafref
    |  |  |        |           +--:(path-request-ref)
    |  |  |        |              +-- path-request-ref    leafref