Fix endurance failures

Fix endurance failures

- endurance test failed since it exited with 'Unsucessful' termination
  because teardown.sh  was not able to remove CPS images (cps-and-nmcp,
policy-executor-stub). The tag 'latest' was used for both pipelines at
the same time: Regular KPI and Endurance
- teardown algorithm changed: it only remove cps images having 'Snapshot' tag.
- dmi-stub removed from the image list since it should always use the
  Snapshot version in the deployment!

Issue-ID: CPS-2870

Change-Id: I1a7d6dbf717e2686c70d845e6f44c7efb1171dae
Signed-off-by: halil.cakal <halil.cakal@est.tech>