commitlog: Always abort replenish queue on loop exit

Fixes #28678

If replenish loop exits the sleep condition, with an empty queue,
when "_shutdown" is already set, a waiter might get stuck, unsignalled
waiting for segments, even though we are exiting.

Simply move queue abort to always be done on loop exit.

Closes scylladb/scylladb#28679

(cherry picked from commit ab4e4a8ac7)

Closes scylladb/scylladb#28691

db/commitlog/commitlog.cc

@@ -1985,13 +1985,13 @@ future<> db::commitlog::segment_manager::replenish_reserve() {
             }
             continue;
         } catch (shutdown_marker&) {
-            _reserve_segments.abort(std::current_exception());
             break;
         } catch (...) {
             clogger.warn("Exception in segment reservation: {}", std::current_exception());
         }
         co_await sleep(100ms);
     }
+    _reserve_segments.abort(std::make_exception_ptr(shutdown_marker()));
 }
 
 future<std::vector<db::commitlog::descriptor>>