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.

{
    assert(pindexNew->pprev == chainActive.Tip());
    
    int64_t nTime1 = GetTimeMicros();
    CBlock block;
    if (!pblock) {
        if (!ReadBlockFromDisk(block, pindexNew, chainparams.GetConsensus()))
            return AbortNode(state, "Failed to read block");
        pblock = &block;
    }
    
    int64_t nTime2 = GetTimeMicros(); nTimeReadFromDisk += nTime2 - nTime1;
    int64_t nTime3;
    LogPrint("bench", "  - Load block from disk: %.2fms [%.2fs]\n", (nTime2 - nTime1) * 0.001, nTimeReadFromDisk * 0.000001);
    {
        CCoinsViewCache view(pcoinsTip);
        bool rv = ConnectBlock(*pblock, state, pindexNew, view, chainparams);
        GetMainSignals().BlockChecked(*pblock, state);
        if (!rv) {
            if (state.IsInvalid())
                InvalidBlockFound(pindexNew, state);