function validateWebsiteHeader(header) {
    return (!header || header.startsWith('/') ||
    header.startsWith('http://') || header.startsWith('https://'));
}
validateWebsiteHeader description]
@param  {string} header - value of
x-amz-website-redirect-location header on a put
object (or similar request -- initiate mpu, object copy)
@return {boolean}        true if valid, false if not