Are fees enabled in cashback_test?

_From @theoreticalbts on November 24, 2015 16:56_

Looks like 8c91d17301a942a72260b19b421bab799701d753 removed `enable_fees()` call from `cashback_test`. This test needs to be evaluated whether the fees are still nonzero, or if this commit inadvertently disabled the fees that are supposed to be tested.

_Copied from original issue: cryptonomex/graphene#461_

Search the repository for cashback_test and inspect the change at commit 8c91d17301a942a72260b19b421bab799701d753. Run the cashback_test and determine whether fees are still nonzero and covered by the test; done means the test verifies the intended fee behavior.

Written by the indexing model from the issue text.