[btcsuite/btcd] 09874f: Fix dropaddrindex flag usage message

[Michail Kargakis]

  Branch: refs/heads/master
  Home:   https://github.com/btcsuite/btcd
  Commit: 09874f1e9115b56573168cf2d310357356c9d80a
      
https://github.com/btcsuite/btcd/commit/09874f1e9115b56573168cf2d310357356c9d80a
  Author: Michail Kargakis <karga...@protonmail.ch>
  Date:   2015-11-23 (Mon, 23 Nov 2015)

  Changed paths:
    M config.go

  Log Message:
  -----------
  Fix dropaddrindex flag usage message