Next patches will stop using compaction manager from table_for_tests in
favor of external one (spoiler: the one from sstables::test_env), thus
the compaction manager would outsurvive the table_for_tests object and
the table object wrapped by it. So in order for the table_for_tests to
stop correctly, it also needs to stop the wrapped table too.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>