When importing, turn off auto-compute.

Turn off auto-recompute on Import: When importing a large list of devices, it might be helpful (less churn on Conductor, thus faster) to turn off auto-compute for all smart groups until the load is done. Then, a single recompute can be done at the end as auto-compute is checked and the DG is saved. This is analogous to turning off indexing when doing many inserts into a RDBMS.