fixes #6830 - add host search on compute_resource_id used in 1.5 auth migrations

To reproduce this:

1. check out 1.4-stable
1. add a CR
1. add a non-admin user
1. edit the user, under Filters, set "must be" on the CR
1. check out develop or this branch
1. rake db:migrate

Usually it fails as compute_resource_id is an unknown search and db/migrate/20140219183343_migrate_permissions.rb tries to create filters with it.

(Warning, running db:seed seems to fail for me due to #6873, but migration is fine.)