Explicitly specifies cm_api version in CDH plugin

We set CM_API_VERSION value in cloudera_utils.py, and in function
get_api_client, we add augment version to api_client.ApiResource
whose default value is CM_API_VERSION. Currently this value is set
to 7.

Closes-Bug: #1387960
Change-Id: I54e19c0c39357c410b070df1315ec3a7eb68740d