Comment 3 for bug 1799298

Change abandoned by Matt Riedemann (<email address hidden>) on branch: master
Review: https://review.openstack.org/624778
Reason: The join in security_groups should be trivial since the table should be empty in neutron cases, and when getting base metadata we also return the password which is stored in instance.system_metadata, so pre-joining instance_system_metadata is actually something we should be doing when we pull the instance from the cell database - it's used more than just vendordata v2 requests, which makes this change essentially not worthwhile.

We either need to optimize how we do the system_metadata joins in the sqlalchemy API code, or we need to reconsider how we store the instance password (move it out of system_metadata).