Provide 'max_connections' tunable in 'postgresql' chef recipe.

It was also added to the Crowbar proposal, so that the value can be adjusted. This choice
should be based on the amount of (Nova) compute nodes to deploy.
Merge pull request #1 from SUSE-Cloud/release/essex-hack-suse/master

Provide 'max_connections' tunable in 'postgresql' chef recipe.