We'd like that to simplify the soon-to-be-introduced
sstable_mutation_reader::close error handling path.
close_index_list can be marked noexcept since parallel_for_each is,
with that index_reader::close can be marked noexcept too.
Note that since reader close can not fail
both lower and upper bounds are closed (since
closing lower_bound cannot fail).
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
6a82e9f4be