Remove [database]connection defaulting
Remove [database]connection defaulting

The config documentation says that the [database]connection config is
defaulted to None but in reality the nova code defaulted it to a local
sqlite database. This is clearly wrong as:

* Nobody wants to run nova with sqlite outside of a test env

* The nova-compute service should never have DB credentials configured

So this patch makes sure that nova does not change the default of this
config option.

Change-Id: I81560b3ba3dbaccdb90b32ed1a3c4ffd8a6283a6
Closes-Bug: #1903824

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