[btcsuite/btcd] c80c8e: Scale up addrman.

[David Hill]

  Branch: refs/heads/master
  Home:   https://github.com/btcsuite/btcd
  Commit: c80c8e7fe9000d887e1e7b9e22595f1b50d8de23
      
https://github.com/btcsuite/btcd/commit/c80c8e7fe9000d887e1e7b9e22595f1b50d8de23
  Author: David Hill <dh...@mindcry.org>
  Date:   2015-04-06 (Mon, 06 Apr 2015)

  Changed paths:
    M addrmgr/addrmanager.go

  Log Message:
  -----------
  Scale up addrman.

This change was suggested as Countermeasure 6 in
Eclipse Attacks on Bitcoin’s Peer-to-Peer Network, Ethan
Heilman, Alison Kendler, Aviv Zohar, Sharon Goldberg. ePrint Archive
Report 2015/263. March 2015.

This mimics Bitcoin Core commit 1d21ba2f5ecbf03086d0b65c4c4c80a39a94c2ee