spec says:
```
ratio of peer responses after which speculation is used. Set to 1 to disable.
speculation-threshold = 1
```

However, code would only trigger after *more* than the threshold is met.

example:
4 shardgroups.
threshold = 0.75
imagine after 3 shardgroups have returned, you would expect the
speculation to kick in.

However, the logic would flow like this:

percentReceived = 1 - (1/4) = 3/4 = 0.75
if percentReceived > speculationThreshold then speculate
if 0.75 > 0.75 -> no speculation!.

It would wait until another shard returns (in this case, until all shard
groups return)

also if threshold=1, bypass speculation logic more explicitly