Unhardcode nova database connection parameters

[database]/[api_database]
idle_timeout = 180
min_pool_size = 100
max_pool_size = 700
max_overflow = 100
retry_interval = 5
max_retries = -1
db_max_retries = 3
db_retry_interval = 1
connection_debug = 10
pool_timeout = 120

Change-Id: I4bfa9ea7fdd1b91c0b43300df49ba79897bc7392
Related-Prod: PROD-26294
5 files changed