Juju attempts to use AWS availability zones with no default subnet

[Aaron Bentley]

Juju does not specify subnets, so it requires a default subnet to exist. But it does not verify that one exists. If no default subnet exists, you get something like this:

$ juju status -e test-release-aws-old
environment: test-release-aws-old
machines:
  "0":
    agent-state: started
    agent-version: 1.20.10
    dns-name: ec2-54-173-176-69.compute-1.amazonaws.com
    instance-id: i-4e6edba2
    instance-state: running
    series: precise
    hardware: arch=amd64 cpu-cores=1 cpu-power=300 mem=3840M root-disk=8192M
    state-server-member-status: has-vote
  "1":
    agent-state: started
    agent-version: 1.20.10
    dns-name: ec2-54-165-191-75.compute-1.amazonaws.com
    instance-id: i-9a88d07b
    instance-state: running
    series: precise
    hardware: arch=amd64 cpu-cores=1 cpu-power=300 mem=3840M root-disk=8192M
  "2":
    agent-state: pending
    dns-name: ec2-54-174-154-12.compute-1.amazonaws.com
    instance-id: i-5ce1c3b6
    instance-state: pending
    series: precise
    hardware: arch=amd64 cpu-cores=1 cpu-power=300 mem=3840M root-disk=8192M
  "3":
    agent-state-info: 'cannot run instances: No default subnet for availability zone:
      ''us-east-1e''. (InvalidInput)'
    instance-id: pending
    series: precise
  "4":
    agent-state-info: 'cannot run instances: No default subnet for availability zone:
      ''us-east-1e''. (InvalidInput)'
    instance-id: pending
    series: precise
  "5":
    agent-state-info: 'cannot run instances: No default subnet for availability zone:
      ''us-east-1e''. (InvalidInput)'
    instance-id: pending
    series: precise
services: {}

[Andrew Wilkins (axwalk)]

Duplicate of lp:1388860. Not sure why the "affects 1.20" got removed. It is clearly still affected. I'll add it back in.