[test_operator] enable tempest-viz tool

Tempest-viz is a tool similar to stackviz, which generate a very nice
html output for tempest, based on subunit. This patch, adds the tool
itself in the test_operator role, and execut it generating the html
file. The main difference between this and stackviz, is that the subunit
is inserted directly into html, which means you don't need any of the
old fancy angular.js libraries and everything is done in one single html
file.

Signed-off-by: Arx Cruz <arxcruz@redhat.com>
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: 2 people