Removed EventBasedHazardCalculatorTestCase

The code here is already covered in the QA tests (which are fast). It is important to remove them because they slow down the development everytime the details of the internal implementation change, whereas the QA test are just fine. See https://bugs.launchpad.net/oq-engine/+bug/1372833.
https://ci.openquake.org/job/zdevel_oq-engine/702