Only disconnect from db pool when size is increasing

[jturel]

The first request to hit the server that initializes dynflow is excruciatingly long. It turns out that dynflow disconnects the db pool before maybe increasing the pool size. In katello devel the database.yml pool size matches dynflow's target size which highlights the problem.

Ping illustrates it perfectly:

Before:

foreman_tasks:
    Status:          ok
    Server Response: Duration: 10137ms

After:

foreman_tasks:
    Status:          ok
    Server Response: Duration: 117ms

[jturel]

@adamruzicka what do you think?

[adamruzicka]

In general I don't have any objections, thank you for polishing something that has been sitting there for almost a decade.

The comments are not hard requirements, but rather "while we're at it"-style comments

[adamruzicka]

Looks good

[adamruzicka]

Thank you @jturel !