Add CORS max age annotation

[sagikazarmark]

What this PR does / why we need it: Currently the Access-Control-Max-Age header cannot be changed when CORS requests are enabled and by default it's set to a very high value which is ignored by browsers. This PR makes the header configurable using annotations.

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #1881

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[k8s-reviewable]

This change is 

[coveralls]

Coverage increased (+0.001%) to 36.698% when pulling b6651fa on sagikazarmark:cors-max-age into 983b994 on kubernetes:master.

[coveralls]

Coverage increased (+0.001%) to 36.698% when pulling b6651fa on sagikazarmark:cors-max-age into 983b994 on kubernetes:master.

[coveralls]

Coverage increased (+0.05%) to 36.75% when pulling b6651fa on sagikazarmark:cors-max-age into 983b994 on kubernetes:master.

[aledbf]

/lgtm

[sagikazarmark]

Thanks