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.

{
    unsigned int nEvicted = 0;
    static int64_t nNextSweep;
    int64_t nNow = GetTime();
    if (nNextSweep <= nNow) {
        
        int nErased = 0;
        int64_t nMinExpTime = nNow + ORPHAN_TX_EXPIRE_TIME - ORPHAN_TX_EXPIRE_INTERVAL;
        map<uint256, COrphanTx>::iterator iter = mapOrphanTransactions.begin();
        while (iter != mapOrphanTransactions.end())
        {
            map<uint256, COrphanTx>::iterator maybeErase = iter++;
            if (maybeErase->second.nTimeExpire <= nNow) {
                nErased += EraseOrphanTx(maybeErase->second.tx.GetHash());
            } else {
                nMinExpTime = std::min(maybeErase->second.nTimeExpire, nMinExpTime);
            }