Fixed #13319 , Incorrect method return value in \Magento\Shipping\Model\Carrier\AbstractCarrier::getTotalNumOfBoxes()

[cedmudit]

Fixed magento#13319 , Incorrect method return value in \Magento\Shipping\Model\Carrier\AbstractCarrier::getTotalNumOfBoxes()

added type casting and updated function comment..

Please see the method getTotalNumOfBoxes() in \Magento\Shipping\Model\Carrier\AbstractCarrier: https://github.com/magento/magento2/blob/2.2.2/app/code/Magento/Shipping/Model/Carrier/AbstractCarrier.php#L512-L531

Incoming $weight parameter is not checked to be integer. Moreover, even if it is, you can still get a float result when $weight > $maxPackageWeight since these are both arbitrary numbers.

This method is a member of AbstractCarrier class commonly used for 3-rd party implementations of the Shipmen Carrier SPI and might be used by 3rd-party developers in their modules.
In order to apply proper validation and\or rounding around the method's return results, it would be helpful to see the actual return value in PHPDocs which are commonly used by IDEs when providing hints, for example here: http://take.ms/9dnaD

Additionally, the method name is severely misleading: it implies the method is a getter, however it can modify object's internal state. Moreover, the value returned is in fact what seems to be an average weight of a box, not "Total number of boxes" as one might assume.

Backward Compatibility: Please note that Magento's USPS implementation expects float return value, implying internal knowledge of the method: https://github.com/magento/magento2/blob/2.2.2/app/code/Magento/Usps/Model/Carrier.php#L341
If any rounding is to be added, it should probably be done via a new extra method, deprecating the old one (if at all)

Preconditions

1. Magento CE 2.1.10, Magento CE 2.2.2
2. PHP 7.0.18

Steps to reproduce

1. Open file app/code/Magento/Shipping/Model/Carrier/AbstractCarrier.php
2. Scroll down to getTotalNumOfBoxes method

Expected result

1. Observe correct return type "float" declared in PHPDoc block
   OR proper rounding applied to the $weight variable.

Actual result

1. Observe incorrect return type "int" declared in PHPDoc block
   AND no rounding applied to $weight variable

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)