fix redundance errors "The input does not appear to be a valid date" show twice

[samsonasik]

Fix The input does not appear to be a valid date that show twice.

[weierophinney]

Please add a unit test for this; it's hard to tell what exactly this fix accomplishes currently.

[samsonasik]

@weierophinney : I added a unit test, and the result of markup of element rendered is success. not twice. but if :

if (false === $date || $errors['warning_count'] > 0) {
is in the line of 131 in Zend\Validator\Date, the error that rendered by formRow() helper show twice like this :

http://samsonasik.files.wordpress.com/2012/10/screen-shot-2012-10-03-at-12-16-13-pm.png

and if i remove
(false === $date)
and run
if ($errors['warning_count'] > 0) {
the error show Once only.

[samsonasik]

@weierophinney : how about :

if ($errors['warning_count'] > 0) {
    $this->error(self::INVALID_DATE); 
} 
if ($date === false) {
    $this->error(self::INVALID_DATE);
}
if ($this->error(self::INVALID_DATE)) {
    return false;
}

OR, what about :

if ($date === false && $errors['warning_count'] > 0) {
    $this->error(self::INVALID_DATE); 
}

The && operator fix this problem.
I try both that and correct the problem. the return is in the last, not early ;).
If you agree, i will re-request the pull.