b295335798
The current default value of stage_dir does not match the valid
default from zuul-jobs, which causes stackviz to be skipped when
stage_dir is not overwritten, which is the case in all CI jobs.
Setting default and docs to "{{ ansible_user_dir }}".
Change-Id: I9fd3f8541c8e3fbc406c5e5c0c5fe8427bf74112