[btcsuite/btcd] 8a4a87: Ignore getheaders requests if not synced.

[David Hill]

  Branch: refs/heads/master
  Home:   https://github.com/btcsuite/btcd
  Commit: 8a4a875e9d4d113ebab25b22e97050508fa810d8
      
https://github.com/btcsuite/btcd/commit/8a4a875e9d4d113ebab25b22e97050508fa810d8
  Author: David Hill <dh...@mindcry.org>
  Date:   2015-07-20 (Mon, 20 Jul 2015)

  Changed paths:
    M peer.go

  Log Message:
  -----------
  Ignore getheaders requests if not synced.

This mimics Bitcoin Core commit a1ba0778dd3c784046dea334e5d39f37eca264f7