Improve rebuild tests in test_server_actions

Rebuild tests rebuild the class level server which
is used by other tests also and they rebuild it
again on the original image. If anything goes
wrong with the class level server then we do recreate
the server in setup of each test.

Doing so much things on server needed by other tests
and recreate them in setup is too much. Instead of
rebuilding the class level server, let's create its
own server and perform the rebuild.

Also, this test does two ssh validation after rebuild
so removing the one.

This might help the issue where test_rebuild_server_with_volume_attached
is failing in detach volume cleanup due to server not
in active state
- https://zuul.opendev.org/t/openstack/build/2964990aa7ab41caa83c485415fffec5/log/job-output.txt#34435

Change-Id: Ia1a57b4d0127baaa614191cc013115732ca1cceb
1 file changed