Fix missing sql_opts
Fix missing sql_opts

`tox -egenconfig` doesn't work, because
`magnum.db.sqlalchemy.models.sql_opts` is moved to
`magnum.db.sql_opts`.

This fixes it.

Change-Id: Ia617ee0ceae5bff7d745a9b48bfcdf9dfc00e336
Closes-Bug: #1490817

mjbrewer/testindex,mjbrewer/testindex,ArchiFleKs/magnum,eshijia/magnum,eshijia/SUR,Tennyson53/magnum,dimtruck/magnum,Tennyson53/SUR,Tennyson53/SUR,jay-lau/magnum,Tennyson53/magnum,openstack/magnum,Alzon/SUR,mjbrewer/testindex,ArchiFleKs/magnum,annegentle/magnum,eshijia/SUR,annegentle/magnum,openstack/magnum,dimtruck/magnum,Alzon/SUR,eshijia/magnum