backport PR9960 https://github.com/bitcoin/bitcoin/pull/9960/files
3cef950 Trivial: Add const modifier to GetHDChain and IsHDEnabled (NicolasDorier)
Tree-SHA512: 73126689e179d70e6823950b51aae4da0a1e348436bc72338814f3afeec27868bb479d9e8261f86e4fe851e84492778a30c5f1fe76c9d7dd91796d0e38baeaf0