Function 'tempest.test.attr()' has moved to 'tempest.lib.decorators
.attr()' in Pike and will be removed in a future version.
This patch replaces the 'tempest.test.attr()' with the 'tempest.lib
.decorators.attr().'
Change-Id: Ic9254d4a214a05bfb930e6abd4ce6c4988311ea0