Sahara: preparations for job binary internal tests

* create/list/get/delete methods to Sahara API client
  for job binary internals were added
* Method "create_job_binary_internal" was added
* tearDownClass method was expanded

Partially implements: blueprint savanna-api-tests

Change-Id: I1013ce8d93ec44d5d5961bcd887812bdd1c6fcfb
Merge "Sahara: preparations for job binary internal tests"