fix(aws-amplify): preserve default auth providers with repetitive calls of configure

[HuiSF]

Description of changes

Added additional condition check for initializing default auth provider with repetitive calls of Amplify.configure. This fix the following issue:

The following code snippet will remove the default auth providers initialized for option ssr: true.

Amplify.configure(config, { ssr: true });

Amplify.configure({
    ...Amplify.getConfig(),
    Analytics: {
        Kinesis: {
            region: 'us-west-2'
        },
    },
});

Issue #, 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)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[elorzafe]

I wonder this should be private?

[elorzafe]

Looks good

Thanks @HuiSF