'amplify init' ignores specified profile

[musou1500]

Description of changes

Following code seems wrong.

amplify-cli/packages/amplify-provider-awscloudformation/src/system-config-manager.ts

Lines 98 to 100 in 989ec35

	const chain = new CredentialProviderChain();
	const processProvider = () => new ProcessCredentials({ profile: profileName });
	chain.providers.push(processProvider);

This specifies credential provider to load credential of specified profile.
But chain.providers.push appends provider to defaultProviders.
consequently, specified provider runs after defaultProviders processed.

It causes use of unexpected credential (in my case, default profile was used to create stack instead of specified profile).

This PR fix it to not use defaultProviders.

Issue #3, if available

Description of how you validated changes

Checklist

• PR description included
• yarn test passes
• Tests are changed or added
• Relevant documentation is changed or added (and PR referenced)
• New AWS SDK calls or CloudFormation actions have been added to relevant test and service IAM policies
• Pull request labels are added

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