Fix postgres upgrade failures

Fixes https://gitlab.com/gitlab-org/omnibus-gitlab/issues/1726

Includes commits from this MR: https://gitlab.com/gitlab-org/omnibus-gitlab/merge_requests/1114 which use reconfigure to setup the symlinks.

Having the symlinks in the package breaks gitlab package upgrades once you have upgraded your database. So instead the symlinks are created during reconfigure the first time, and then again whenever they need to change.