before this change, we use the format string of
"Can't replace node {} with itself", but fail to include the host id as seastar::format()'s arguments. this fails the compile-time check of fmt, which is yet merged. so, if we really run into this problem, {fmt} would throw before the intended runtime_error is raised -- currently, seastar::log formats the logging messages at runtime, this is not intended.
in this change, we pass `existing_node`, so it can be formatted, and the
intended error message can be printed in log.
Refs 11a4908683
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closesscylladb/scylladb#16342