test_preview_update only create one stack per test

Currently some tests create two stacks, but only require one, which
wastes some time (as much as 20s locally, probably much more in the
gate), so instead just create one stack per test.

Change-Id: I474877becdd64f30abdcc5758c5927ed6b5a13ff
1 file changed
tree: c4f48aa4cd91e1eb3353138c02681404096b8835
  1. common/
  2. functional/
  3. scenario/