Do not return an error code when reserving a node already reserved, as

happens when tbprerun does its thing. Causes experiment creation to
stop, when using delay nodes.

db/nalloc

@@ -29,7 +29,7 @@ foreach my $n (@node_names) {
     $sth = $dbh->query($cmd);
     if ($sth->numrows > 0) {	
       print "You have already reserved node '$n'.\n";
-      $error++;
+      # Do not increment error code since that throws off tbprerun.
     } else {
       print "Someone else has already reserved node '$n'.\n";
       $error++;