Store kubernetes server version after conformance tests

To use with xunit_reporter

Log output example:

  -- Kubernetes server version is stored to ./env_k8s_version:
  export KUBE_SERVER_VERSION=1.10
  export KUBE_SERVER_GIT_VERSION=v1.10.4-4+971831eb5eb3db

Usage example:

  . ./env_k8s_version
  report ... --testrail-suite "[MCP][k8s]Hyperkube ${KUBE_SERVER_VERSION}.x"

Change-Id: Ia27b9e16142d5bb30f5dee5030095c2eb4e8e08c
diff --git a/tcp_tests/managers/k8s/cluster.py b/tcp_tests/managers/k8s/cluster.py
index db7bb18..1531f0d 100644
--- a/tcp_tests/managers/k8s/cluster.py
+++ b/tcp_tests/managers/k8s/cluster.py
@@ -92,6 +92,7 @@
         self.api_autoscaling = client.AutoscalingV1Api(api_client)
         self.api_batch = client.BatchV1Api(api_client)
         self.api_rbac_auth = client.RbacAuthorizationV1Api(api_client)
+        self.api_version = client.VersionApi(api_client)
 
         self.nodes = K8sNodeManager(self)
         self.pods = K8sPodManager(self)