Improved error message about non-unique names in end2end test
Improved error message about non-unique names in end2end test

Details:

* The message so far was dumping the complete list of objects which made the
  message hard to understand. Improved that so that now only the URIs of the
  resources with non-unique names are listed.

Signed-off-by: Andreas Maier <38dbb04957d222ea6ce72de72413b1e55e665472@de.ibm.com>

zhmcclient/python-zhmcclient,zhmcclient/python-zhmcclient