Remove script file provisioning

It doesn't seem to be the case that this is actually necessary.
Remove postgres user related ssh stuff

It should no longer be necessary to give this user ssh access, since
the automation stuff can be scripted using the expect tool.
Remove key provisioning
Setup epel repository and do an update

As separate steps.
Install expect and expectk

These are necessary to automate the postgres initialisation
Remove yum update

This is actually done in the post script in kickstart.
Remove postgres source directory
Add script to initialise postgres