CarrierCompare does not return a correct carriers

In CarrierCompare::getCarriersByCountry(), we are cloning the current cart into a temporary cart.
While cloning, 2 issues come up:
1. id_customer is missing
2. products with attributes (combinations) are missing.
Merge pull request #1 from prtung8888/patch-1

CarrierCompare does not return a correct carriers