[conformal/btcd] 8774a7: Use Errorf when using formatting directives.

[David Hill]

  Branch: refs/heads/master
  Home:   https://github.com/conformal/btcd
  Commit: 8774a77d33c82e0fdf256dbd7a0094bcc2f73089
      
https://github.com/conformal/btcd/commit/8774a77d33c82e0fdf256dbd7a0094bcc2f73089
  Author: David Hill <dh...@conformal.com>
  Date:   2014-08-28 (Thu, 28 Aug 2014)

  Changed paths:
    M addrmgr/addrmanager.go

  Log Message:
  -----------
  Use Errorf when using formatting directives.

Found by go vet.