Addressing Yang doctor review comments

[italobusi]

Addressing some YANG doctor review comments:

• https://mailarchive.ietf.org/arch/msg/ccamp/CqHx1813l9OfKkA_6ijZ5E_zlvs/
• https://mailarchive.ietf.org/arch/msg/ccamp/hevNlzTnh9ra4Ru0q2VwmFmMwU4/

Comments addressed:

• fix otn-tunnel compilation errors
• removing the two groupings in otn-topology

The comments on the prefixes is pending resolution of mailing list discussions.

Other comments are on the draft and outside the scope of this PR.

Co-authored-by: haomianzheng zhenghaomian@huawei.com Co-authored-by agva123 agva123@gmail.com