Changes

testenv: show testsuite results at the end

Show the testsuite results from junit-*.log not after each testenv*.cfg
file is through, but for all of them at the end. This way the results
are in one place when running with multiple configs, we don't need to
scroll to the middle of the huge log to find out what tests passed with
a previous config.

Adjust the podman container stop and restart logic, so the last
container is still running until we use it for showing the results.

Change-Id: Ie4b70724a33932cd98ba0972db37bf72dc8affb8

testenv: more tweaks for container shutdown logic

* Don't do "podman wait" when restarting the container. The idea was to
  really wait before the current container was shutdown before
  restarting one with the same name. But even with the wait we got "the
  container name ... is already in use" errors and so we use different
  names when restarting the container since 6fe837de ("testenv: podman:
  restart_count in container_name"). This means "podman wait" is not
  needed anymore.

* feed_watchdog_loop: change sleep from 5s to 2s, as we wait up to that
  long after the container was shutdown, before testenv stops. 5s is
  quite noticable compared to 2s when running the script locally.

* feed_watchdog_loop: hide stderr of "podman exec" since it will print
  "Error: container ... does not exist in database: no such container"
  during shutdown. This is expected as we stop the container, but it
  looks like an actual error. We already have a more userfriendly
  message "feed_watchdog_loop: podman container has stopped" that will
  appear when the "podman exec" fails during shutdown.

Change-Id: I71721fd41f044817e4021aea045a288f88506f76