Add DB Pool configuration parameters

Use these parameters to control the size of Nova's db connection
pool size. By default the pool is sized between 1-10 connections, with
an unlimited amount of overflow connections. Limit the amount of these
if you like to protect your database server.

Signed-off-by: Christoph Kassen <christoph@kassen.name>
Add DB Pool parameters tests

Ensure that all three values are set with the default values.
This matches the behaviour of the test suite.

Signed-off-by: Christoph Kassen <christoph@kassen.name>
Merge pull request #2 from TelekomCloud/feature/sql_pool

Add DB Pool configuration parameters