Fix the SSL state for databases connections

Fix the SSL state for databases connections

Whenever possible, we use a socket connexion (all postgresql
connections, and a few mysql ones)

When remote (only mysql), we require SSL in the users database (cannot
be enforced globally)

Also, put pam configurations in a correct state

Fixes https://git.immae.eu/mantisbt/view.php?id=89
Fixes https://git.immae.eu/mantisbt/view.php?id=90
Fixes https://git.immae.eu/mantisbt/view.php?id=88