Per-partition rate limiting added a new error type which should be
returned when Scylla decides to reject an operation due to per-partition
rate limit being exceeded. The new error code requires drivers to
negotiate support for it, otherwise Scylla will report the error as
`Config_error`. The existing error code override logic works properly,
however due to a mistake Scylla will report the `Config_error` code even
if the driver correctly negotiated support for it.
This commit fixes the problem by specifying the correct error code in
`rate_limit_exception`'s constructor.
Tested manually with a modified version of the Rust driver which
negotiates support for the new error. Additionally, tested what happens
when the driver doesn't negotiate support (Scylla properly falls back to
`Config_error`).
Branches: 5.1
Fixes: #11517Closes#11518
e69b44a60f