Use memory mode for sqlite in db test
Use memory mode for sqlite in db test

Config option sqlite_db is deprecated in
0a1bae9859079fb21a03716be947c5f1da6db0a2, and deprecate argument
sqlite_db in method set_defaults in
https://review.openstack.org/#/c/350945/, should use config option
connection instead. For magnum, we test database with sqlite in
memory mode [1] as below:

CONF.set_default('connection', "sqlite://", group='database')

and don't use config option sqlite_db, so remove unused code.

[1]http://docs.sqlalchemy.org/en/rel_1_0/core/engines.html#sqlite

Change-Id: I69f7d7c1f84b577db1fc2de0e1106b61d1cceac6

ArchiFleKs/magnum,ArchiFleKs/magnum,openstack/magnum,openstack/magnum