[virtlet] Refactor virtlet part

- Remove virtlet roles
- Remove virtlet fixtures due virtlet officially installed as
addon if option is enabled
- Move virtlet core test functions under k8smanager.py
- Add show_step into virtlet tests
- Add checks that virtlet is enabled to the beginning of tests

Change-Id: Ibfb499b29727b367afafc68fa13199db13bcccdf
diff --git a/tcp_tests/tests/system/conftest.py b/tcp_tests/tests/system/conftest.py
index 9089870..9aa021e 100644
--- a/tcp_tests/tests/system/conftest.py
+++ b/tcp_tests/tests/system/conftest.py
@@ -23,8 +23,6 @@
 from tcp_tests.fixtures.oss_fixtures import *  # noqa
 from tcp_tests.fixtures.decapod_fixtures import *  # noqa
 from tcp_tests.fixtures.stacklight_fixtures import *  # noqa
-from tcp_tests.fixtures.virtlet_fixtures import *  # noqa
-from tcp_tests.fixtures.virtlet_ceph_fixtures import *  # noqa
 from tcp_tests.fixtures.k8s_fixtures import *  # noqa
 
 
@@ -62,9 +60,5 @@
     'sl_deployed',
     # k8s fixtures
     'k8s_actions',
-    'k8s_deployed',
-    'virtlet_actions',
-    'virtlet_deployed',
-    'virtlet_ceph_actions',
-    'virtlet_ceph_deployed'
+    'k8s_deployed'
 ])