Config option sqlite_db is deprecated for removal[1],
and isn't used in gce-api, so don't need set its default value.
[1]https://github.com/openstack/oslo.db/blob/\
0a1bae9859079fb21a03716be947c5f1da6db0a2/oslo_db/options.py#L17
Change-Id: Ib176bca26d2bb49e301fdd71a923886be32a0339