Acecssing this member directly is deprecated, migrate code to use {get,set}_query_param() and friends instead.
Fixes: https://github.com/scylladb/scylladb/issues/26023
Preparation for seastar update, no backport required.
Closesscylladb/scylladb#26024
* github.com:scylladb/scylladb:
treewide: move away from accessing httpd::request::query_parameters
test/pylib/s3_server_mock.py: better handle empty query params