[backend] bs_sched revert number of projpacks for full scan

reverts part of 64ae5c9
the trade off is between doing a full scan or cleaning
up data for all dirty projects. it looks like the optimum
is a lot closer to 200 (or even lower than that) than the
1000 the old patch used.

src/backend/BSSched/ProjPacks.pm

@@ -834,7 +834,7 @@ sub setup_projects {
 
   my $t1 = Time::HiRes::time();
   my $projids_todo_cnt = scalar(@{$projids_todo || []});
-  undef $projids_todo if $projids_todo_cnt > 1000;	# removing old stuff takes too long
+  undef $projids_todo if $projids_todo_cnt > 200;	# removing old stuff takes too long
 
   my @projids_todo;
   if ($projids_todo) {