Remove checking of non empty resp body for 204

In case API respond with 204 status code which mean empty response
body, test case does not need to explicitly check the empty response
body. General check for the same is done in rest_client'
response_checker()

This patch removes those checks of empty response body in tests.

Change-Id: I34537968c1a58e6e73022637a71a3a8091ac214c
3 files changed