~/.aws/config profiles with dots not supported with assumed role profiles

**Describe the bug**
the following profile project-dev cause the error "Error: Profile configuration is missing for: project-dev"

```
[profile default.dev]
aws_access_key_id=****
aws_secret_access_key=****
region=us-east-1

[profile default.admin]
aws_access_key_id=****
aws_secret_access_key=****
region=us-east-1

[profile project-dev]
source_profile=default.dev
role_arn=arn:aws:iam::****:role/Dev
region=us-east-1
```

**To Reproduce**
Steps to reproduce the behavior:
1. amplify init
2. select default values
3. When prompted for using profile: Y
4. Select project-dev
4. See error

**Expected behavior**
Use the profile, the aws cli has no problem with this config

**Additional context**
The problem is from https://github.com/aws-amplify/amplify-cli/blob/master/packages/amplify-provider-awscloudformation/lib/system-config-manager.js#L246

the object returned from ini.parse will look like:
```
{
'profile default' : {
dev: {
aws_access_key_id: ***
aws_secret_access_key: ***
},
admin: {
aws_access_key_id: ***
aws_secret_access_key: ***
}
'profile project-dev': {
source_profile: 'default.dev'
role_arn: 'arn:aws:iam::****:role/Dev'
region: 'us-east-1'
}