ansible-test: Fix new findings

ERROR: Found 6 pylint issue(s) which need to be resolved:
ERROR: plugins/modules/ipaserver_prepare.py:395:4: invalid-name: Variable name "e" doesn't conform to snake_case naming style
ERROR: roles/ipaserver/library/ipaserver_prepare.py:395:4: invalid-name: Variable name "e" doesn't conform to snake_case naming style
ERROR: roles/ipaserver/module_utils/ansible_ipa_server.py:333:12: invalid-name: Variable name "ds" doesn't conform to snake_case naming style
ERROR: roles/ipaserver/module_utils/ansible_ipa_server.py:348:12: invalid-name: Variable name "ds" doesn't conform to snake_case naming style
ERROR: roles/ipaserver/module_utils/ansible_ipa_server.py:361:12: invalid-name: Variable name "ip" doesn't conform to snake_case naming style
ERROR: roles/ipaserver/module_utils/ansible_ipa_server.py:364:12: invalid-name: Variable name "e" doesn't conform to snake_case naming style

e has been replaced with err, ds with _ds, ip with _ip.