Some readability fixup for dbconfig

During the backport of the previous patch, Diane Fleming suggested
some fixes: https://review.openstack.org/#/c/97552/. This patch
applies it to the master branch first.

Change-Id: Ie26552669cd4d479d82eaeaa99c986bf636453d3
Backport: icehouse
Merge "Some readability fixup for dbconfig"