The test creates all driver sessions by itself. As a consequence, all
sessions use the default request timeout of 10s. This can be too low for
the debug mode, as observed in scylladb/scylla-enterprise#5601.
In this commit, we change the test to use `cluster_con`, so that the
sessions have the request timeout set to 200s from now on.
Fixesscylladb/scylla-enterprise#5601
This commit changes only the test and is a CI stability improvement,
so it should be backported all the way to 2024.2. 2024.1 doesn't have
this test.
Closesscylladb/scylladb#25510