Skip Job Cost Calulations on Non-Cloud Platforms

When 'job-cost.sh' is ran on a VM not initialized with cloud-init, or
running in OpenStack, attempts to read '/run/cloud-init/result.json'
will fail causing the job to become unsable.

This change adds a check for any relevant files to the beginning of
'job-cost.sh' in order to skip the calculation on VMs not running on
either AWS or OpenStack.

Change-Id: I878adee1ba3ceeffa574a1b1c7ae103811344123
Signed-off-by: Trevor Bramwell <tbramwell@linuxfoundation.org>