Limit not always respected by query cache

[kaidaguerre]

Following sequence results in incorrect (limited) data being returned

> select name from aws_s3_bucket;
> .cache clear
> select name from aws_s3_bucket limit 5;
> select name from aws_s3_bucket;

this results in the unlimited query returning limited data

This is caused by the fact that the result key does not include the limit - therefore multiple index items referred to the same result key