backport PR10115 https://github.com/bitcoin/bitcoin/pull/10115/files
185c7f0 Avoid reading the old hd master key during wallet encryption (Matt Corallo)
Tree-SHA512: b744e8490c0e948355bb77b2695902bb99f89a68af46aa2be9120bd2ccf3c340eb8a56340fec117f9a935192298028945c9b18120ee6b8b23e7da8ffdb635745
(parent was backported in D927)