Adds support for CORS on error responses and Authorization header

[canhnt]

1. This PR supports for CORS error responses, e.g., 4xx or 5xx.

When CORS responses return with error codes, CORS headers are not added properly because 'add_header' directives by default do not add to the response header [1]

[1] http://nginx.org/en/docs/http/ngx_http_headers_module.html#add_header

2. This PR also supports CORS with 'Authorization' header, which is often used to store JWT token.

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[k8s-reviewable]

This change is 

[canhnt]

signed CLA!

[coveralls]

Coverage remained the same at 43.046% when pulling 46a42a2 on canhnt:master into 116fbe8 on kubernetes:master.

[coveralls]

Coverage remained the same at 43.046% when pulling 46a42a2 on canhnt:master into 116fbe8 on kubernetes:master.

[aledbf]

/lgtm

[aledbf]

@canhnt thanks!