Don't link pg_config for PostgreSQL
Don't link pg_config for PostgreSQL

On Debian systems this change is destructive. It creates a symlink
on top of the `pg_config` binary which exists.

This was caused by the recent upgrade of the Puppet PostgreSQL module
from 3.4.1 to 4.1.0 [1]: "Link pg_config binary into /usr/bin"

[1]: https://github.com/puppetlabs/puppetlabs-postgresql/blob/master/CHANGELOG.md#2014-09-03---supported-release-400

Subsequently MODULES-1485 [2] was opened which correctly identified that
this change was very destructive on Debian systems.

[2]: https://tickets.puppetlabs.com/browse/MODULES-1485

This has caused our PostgreSQL clients (including the development VM)
to stop being able to install the `pg` gem.

It can be fixed by removing the postgresql-common packages and allowing
Puppet to re-run to reinstall them:

```
sudo rm /usr/bin/pg_config
sudo apt-get remove postgresql-client-9.3 postgresql-client-common
```

The change to the PostgreSQL module has been fixed in 4.2.0 [3]

[3]: https://github.com/puppetlabs/puppetlabs-postgresql/blob/master/CHANGELOG.md#2015-03-10---supported-release-420

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