Increase the value of the max-networking-io-control-blocks option for the cpp tests as it is too low and causes flakiness as seen in vector_search.vector_store_client_test.vector_store_client_single_status_check_after_concurrent_failures: ``` seastar/src/core/reactor_backend.cc:342: void seastar::aio_general_context::queue(linux_abi::iocb *): Assertion `last < end` failed. ``` See also https://github.com/scylladb/seastar/issues/976 Fixes #27056 Signed-off-by: Benny Halevy <bhalevy@scylladb.com> Closes scylladb/scylladb#27117