database: Don't keep so many connections open and idle

database: Don't keep so many connections open and idle

Since we usually peak briefly, we will fork a lot of PostgreSQL
processes that we will never need again. In order to avoid wasting too
much memory, we close those connections quicker, but at least 8 open so
that new tasks will quickly be able to acquire a database connection.

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>