Execute scripts as root in EC2

Kludgy; should investigate if image we're building from will allow
direct root access.
Don't attempt to set hwclock on EC2
Ensure appropriate failures in shell scripts
Run 'yum upgrade'
Close stdin on all scripts

I think this will force a failure of programs (like yum) that may
prompt for input unless told not to.  I get bitten by this
occasionally.
Ensure new kernel boots by default