Do not bias outgoing connections towards fresh addresses

This change was suggested as Countermeasure 2 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.

src/addrman.cpp

@@ -63,8 +63,6 @@ double CAddrInfo::GetChance(int64_t nNow) const
     if (nSinceLastTry < 0)
         nSinceLastTry = 0;
 
-    fChance *= 600.0 / (600.0 + nSinceLastSeen);
-
     // deprioritize very recent attempts away
     if (nSinceLastTry < 60 * 10)
         fChance *= 0.01;