As segwit is active on testnet, blocks will only be downloaded from NODE_WITNESS peers. Though, exactly those peers are disconnected after `BLOCK_STALLING_TIMEOUT = 2` seconds. I am running master (6e6ab2c)

This behavior is consistent across restarts. Sample [debug.log](http://pastebin.ubuntu.com/23058327/) and [getchaintips](http://pastebin.ubuntu.com/23058325/).

It is possible that I shot my own foot at some point, but it seemed smelly enough to create an issue.

if (pindex == pindexFirstNotTreeValid) pindexFirstNotTreeValid = NULL;
            if (pindex == pindexFirstNotTransactionsValid) pindexFirstNotTransactionsValid = NULL;
            if (pindex == pindexFirstNotChainValid) pindexFirstNotChainValid = NULL;
            if (pindex == pindexFirstNotScriptsValid) pindexFirstNotScriptsValid = NULL;
            
            CBlockIndex* pindexPar = pindex->pprev;
            
            std::pair<std::multimap<CBlockIndex*,CBlockIndex*>::iterator,std::multimap<CBlockIndex*,CBlockIndex*>::iterator> rangePar = forward.equal_range(pindexPar);
            while (rangePar.first->second != pindex) {
                assert(rangePar.first != rangePar.second); 
                rangePar.first++;
            }
            
            rangePar.first++;
            if (rangePar.first != rangePar.second) {
                
                pindex = rangePar.first->second;
                break;
            } else {
                
                pindex = pindexPar;
                nHeight--;
                continue;
            }
        }
    }
    
    assert(nNodes == forward.size());
}
std::string GetWarnings(const std::string& strFor)