Deletes all of the existing buildpack caches in the blobstore

def clean_blobstore_cache(self):
        """Deletes all of the existing buildpack caches in the blobstore"""
        url = self.api_url + self.blobstores_builpack_cache_url
        resp, rcode = self.request('DELETE', url)
        if rcode != 202:
            raise CFException(resp, rcode)
        return resp