ASM-2659 Add backend support for NTP for Red Hat deployments

Updated the kickstart and post_install ERB files to include the timezone and NTP configuration during the initial installation.
This will take care of the case where servers are reported to have time lag between resulting in the failure of puppet agent not check-in with puppet master
This will need to be templatized to support rhel7 as well. Here's an example:

https://github.com/dell-asm/razor-server/blob/a3ce60105072c5deccb49127f35a40f369c2d0f2/tasks/redhat/post_install.erb#L51