Mark chunks as saved after saving them

Prevents re-saving them again later.

patches/server/Rewrite-chunk-system.patch

@@ -10845,6 +10845,8 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 +
 +                    task.queue();
 +
++                    chunk.setUnsaved(false);
++
 +                    return true;
 +                } catch (final ThreadDeath death) {
 +                    throw death;
@@ -10863,6 +10865,7 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 +            } else {
 +                RegionFileIOThread.scheduleSave(this.world, this.chunkX, this.chunkZ, save, RegionFileIOThread.RegionFileType.CHUNK_DATA);
 +            }
++            chunk.setUnsaved(false);
 +        } catch (final ThreadDeath death) {
 +            throw death;
 +        } catch (final Throwable thr) {