// The responses for fetching the object when If-Modified-Since
// and If-Unmodified-Since headers set are validated.
// If-Modified-Since - Return the object only if it has been modified since the specified time, else return a 304 (not modified).
// If-Unmodified-Since - Return the object only if it has not been modified since the specified time, else return a 412 (precondition failed).
func (s *TestSuiteCommon) TestHeadOnObjectLastModified(c *check) {