Fix test failure by ordering leaf-lists

Fix test failure by ordering leaf-lists

YANG specifies two ways that leaf-lists can be ordered:
- ordered-by user: original order in JSON is preserved
- ordered-by system (default): it is up to the system how to order

For leaf-lists to preserve same order as the JSON, the Yang module
must specify 'ordered-by user'. To ensure consistent behaviour even
when system ordering is used, the leaf-list is sorted during parsing.

- Add 'ordered-by user' to authors field in bookstore.yang
- Sort leaf-list during parsing when using 'ordered-by system'
- Add new tests to verify ordering

Issue-ID: CPS-2057
Signed-off-by: danielhanrahan <daniel.hanrahan@est.tech>
Change-Id: I6ab688ec2fa4a22182e853d1a8b26642f278c40a