before we support incremental repair, these is no point have the
code path setting / getting it. and even worse, it incurs confusion.
so, in this change, we
* just set the field to 0,
* drop the corresponding field in metadata_collector, as we never
update it.
* add a comment to explain why this variable is initialized to 0
Fixes#16098
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closesscylladb/scylladb#16169