[conformal/btcwallet] c51cbb: Refactor len(w.secret) != 32

[Jimmy Song]

  Branch: refs/heads/master
  Home:   https://github.com/conformal/btcwallet
  Commit: c51cbb33325c951cdbdb90e7ff0ca66c3e400675
      
https://github.com/conformal/btcwallet/commit/c51cbb33325c951cdbdb90e7ff0ca66c3e400675
  Author: Jimmy Song <jaej...@gmail.com>
  Date:   2014-03-20 (Thu, 20 Mar 2014)

  Changed paths:
    M wallet/wallet.go

  Log Message:
  -----------
  Refactor len(w.secret) != 32

Now using w.IsLocked() for all instances of above.
Also changed one other place where the logic had to be reversed
in nextChainedAddress (len(w.secret) == 32 was the condition).