[btcsuite/btcd] a109be: mempool: unexport the mutex

[David Hill]

  Branch: refs/heads/master
  Home:   https://github.com/btcsuite/btcd
  Commit: a109bea3f17c496a7622bca4e81f2c33015976ce
      
https://github.com/btcsuite/btcd/commit/a109bea3f17c496a7622bca4e81f2c33015976ce
  Author: David Hill <dh...@mindcry.org>
  Date:   2016-08-23 (Tue, 23 Aug 2016)

  Changed paths:
    M mempool/mempool.go

  Log Message:
  -----------
  mempool: unexport the mutex

callers should not need to lock/unlock the mempool themselves.