db: Register database config options ourselves
db: Register database config options ourselves

Deep copy the database options, allowing us to reuse them exactly. This
was actually suggested in I7b74c4bb4a3edc335523c62ec63e57fdd5c51f39,
which added the current code but was rejected at the time because it
"would make our lives harder when we need to deprecate those cloned API
DB opts." I don't know why we'd ever want to deprecate the cloned
options so I see no reason not to take this approach now. Doing so
results in less complicated/weird code and also sets us up nicely for
future changes that'll remove some of the now unnecessary abstraction
layers provided by oslo.db.

Change-Id: I714dce969088e17caaa1daddc881ebca6834e0f1
Signed-off-by: Stephen Finucane <4725dc7f3632bf126d9fbdc30c347e91e8d2fe16@redhat.com>

openstack/nova,openstack/nova,mahak/nova,mahak/nova,mahak/nova,openstack/nova