Honor the credential provider chain on all CRUD operations with copilot

[adamjkeller]

When I attempt to delete an app or env in copilot (using the ec2 instance role as my credential source), I receive the following error:

$ copilot app delete
Are you sure you want to delete application ecsworkshop? Yes
✘ read AWS config file /home/ec2-user/.aws/config, you might need to run aws configure first: load ini file /home/ec2-user/.aws/config: open /home/ec2-user/.aws/config: no such file or directory

My workflow, using the EC2 instance role:

Deleted services underneath the application successfully.
Try to delete the app or the env, both failed with that error.

The workaround is to add this to my aws config:

adam:~/environment/ecsdemo-frontend (master) $ cat ~/.aws/config 
[default]
region = us-west-2
output = json
role_arn = <role-arn-here>
credential_source = Ec2InstanceMetadata