fix an out of bound access in keyListResponseWithCorrectSize

[dhiaayachi]

Fix #647

The function keyListResponseWithCorrectSize truncate the key list until if fit in q.serf.config.QueryResponseSizeLimit / minEncodedKeyLength.

The logic in keyListResponseWithCorrectSize is flawed, for the special case where the list of keys is smaller then the min required size q.serf.config.QueryResponseSizeLimit / minEncodedKeyLength an out of bound access will happen in here

The fix proposed in here is to loop through the minimum of the actual key size and q.serf.config.QueryResponseSizeLimit / minEncodedKeyLength, this will ensure that:

• for normal scenarios where q.serf.config.QueryResponseSizeLimit / minEncodedKeyLength is smaller then the number of keys the logic is unchanged
• for the scenario where the number of keys is smaller then q.serf.config.QueryResponseSizeLimit / minEncodedKeyLength we will start with the full list of key and then try to truncate

[markan]

This looks good to me.