Minor improvements and fixes to #1

[mmeidlinger]

• Add loopback address for server FQDN to /etc/hosts (Error while provisioning EC2 instance #1 )
• Install duplicity via snap rather than pip
• Unique resource names to allow co-existance of cloudformation stacks
• Moving to gp3 and making the root volume size a parameter

[teckdev]

I can confirm that this fixed my issue with creating the instance. Thank you so much!