Refactoring of k8s manager and tests

Changes:
 - Official kubernetes python lib
 - Rewrite k8s api wrapper in OOP manner
 - Use api where its possible instead of cli
 - Remove virtlet code because its can be replaced with pod api
 - Remove unused/oudated manager code
 - Remove bug workaround in k8s upgrade template
 - Remove netchecker obsolete code
 - Remove unfinished test_rbd_flexvolume_driver

Change-Id: I446a240123282196a6ba54f588aea84791f175ba
Related-PROD: PROD-21700
diff --git a/tcp_tests/managers/k8s/__init__.py b/tcp_tests/managers/k8s/__init__.py
index bd76aa7..9a5c573 100644
--- a/tcp_tests/managers/k8s/__init__.py
+++ b/tcp_tests/managers/k8s/__init__.py
@@ -11,10 +11,7 @@
 #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 #    License for the specific language governing permissions and limitations
 
-import urllib3
-
 from tcp_tests.managers.k8s.cluster import K8sCluster
+from tcp_tests.managers.k8s.base import read_yaml_file, read_yaml_str
 
-__all__ = ['K8sCluster']
-
-urllib3.disable_warnings()  # Supress https insecure warning
+__all__ = ['K8sCluster', 'read_yaml_file', 'read_yaml_str', 'read_yaml_url']