Remove deprecated / unused configure_db function

[Flavio Percoco]

The function configure_db, located in the database api, is not being used anywhere in the code but tests. In order to avoid confusions and wrong usage (some bugs have been found around it) it would be better to remove it.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/26737

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/26737
Committed: http://github.com/openstack/glance/commit/d700f24203768211468d4879b5fa93a59fabf9e3
Submitter: Jenkins
Branch: master

commit d700f24203768211468d4879b5fa93a59fabf9e3
Author: Flaper Fesp <email address hidden>
Date: Thu Apr 11 13:49:13 2013 +0200

    Remove unused configure_db function

    DB drivers currently implement a configure_db function that is supposed
    to be used for seting up the environment and getting an engine back from
    it. Since it is not being used anywhere in the code but tests, I removed
    it and modified tests in order to call both functions (setup_db_env and
    get_engine) where/ when needed.

    As pointed out in another bug, it is important to just call setup_db_env
    when instantiating the db_api in order to keep it lazy. AS for
    sqlalchemy get_engine will be called when a session is requested.

    Fixes bug 1167770

    Change-Id: I2ebeb5e8424a4857df21f7c2d5b33e8ae0100c6a