We should fix postgres version

[anayrat]

Due to this task:

ansible-scripts/roles/postgresql/tasks/main.yml

Line 16 in b977744

- postgresql

When the playbook is executed, it installs the latest postgres version. We should indicate postgres'version to avoid that.

[jocelynj]

What is the problem in always installing the latest version?

[anayrat]

Each time a new Postgres version is released, a new version is installed. Thus, we have 3 instances running on osmose1.davintech.ca but only one is used.