There isn't a switch to set this at join time however there are a few workarounds:
1. Prior to joining run the following to set preload-nested-memberships to false in the vas.conf file.
/opt/quest/bin/vastool configure vas vasd preload-nested-memberships false
2. Run the join command like this:
/opt/quest/bin/vastool configure vas vasd preload-nested-memberships false ; /opt/quest/bin/vastool -u admin join
3. Set preload-nested-memberships to false in group policy. The policy will be applied prior to to the memberships being loaded.