Allow EC2 fleet packer instances to run in parallel
Allow EC2 fleet packer instances to run in parallel

Without conflicting over the name of the launch template that they create/delete.

Previously, the launch template name was just hard coded to `packer-fleet-launch-template`, but since AWS enforces unique template names within an account, this caused simultaneously running packer instances to hit template-already-exists errors when creating their templates and race-conditions around deleting the template. Now, the template name is randomly generated on each run, so there should be no conflicts.

ricardclau/packer,ricardclau/packer,tas50/packer,pecigonzalo/packer,paulmey/packer,ricardclau/packer,mitchellh/packer,bryson/packer,hashicorp/packer,bryson/packer,pecigonzalo/packer,grubernaut/packer,pecigonzalo/packer,hashicorp/packer,dave2/packer,timsutton/packer,bryson/packer,grubernaut/packer,rnaveiras/packer,paulmey/packer,paulmey/packer,tas50/packer,bryson/packer,hashicorp/packer,rnaveiras/packer,grubernaut/packer,paulmey/packer,tas50/packer,tas50/packer,grubernaut/packer,bryson/packer,timsutton/packer,dave2/packer,ricardclau/packer,dave2/packer,dave2/packer,bryson/packer,ricardclau/packer,rnaveiras/packer,timsutton/packer,mitchellh/packer,timsutton/packer,grubernaut/packer,dave2/packer,mitchellh/packer,dave2/packer,rnaveiras/packer,mitchellh/packer,pecigonzalo/packer,rnaveiras/packer,mitchellh/packer,timsutton/packer,tas50/packer,hashicorp/packer,paulmey/packer,tas50/packer,timsutton/packer,rnaveiras/packer,paulmey/packer,ricardclau/packer,grubernaut/packer