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.

pindexIter->nDataPos = 0;
            pindexIter->nUndoPos = 0;
            
            pindexIter->nTx = 0;
            pindexIter->nChainTx = 0;
            pindexIter->nSequenceId = 0;
            
            setDirtyBlockIndex.insert(pindexIter);
            
            setBlockIndexCandidates.erase(pindexIter);
            std::pair<std::multimap<CBlockIndex*, CBlockIndex*>::iterator, std::multimap<CBlockIndex*, CBlockIndex*>::iterator> ret = mapBlocksUnlinked.equal_range(pindexIter->pprev);
            while (ret.first != ret.second) {
                if (ret.first->second == pindexIter) {
                    mapBlocksUnlinked.erase(ret.first++);
                } else {
                    ++ret.first;
                }
            }
        } else if (pindexIter->IsValid(BLOCK_VALID_TRANSACTIONS) && pindexIter->nChainTx) {
            setBlockIndexCandidates.insert(pindexIter);
        }
    }
    PruneBlockIndexCandidates();
    CheckBlockIndex(params.GetConsensus());
    if (!FlushStateToDisk(state, FLUSH_STATE_ALWAYS)) {
        return false;
    }
    return true;
}
void UnloadBlockIndex()