Implemented HW2HW network performance testing

Implemented HW2HW network performance test:
- Added K8S client manager and API methods
- Added method for collecting HW compute nodes
- Improved and extended global config
- Extended requirements.txt, pinned some modules
- Extended and improved SSH methods

Added some small improvements:
- extended .gitignore
- Added some custom exceptions instead of basic ones
- Renamed some classes
- Set iperf v2 to be default for multi-threads tests
- Updated README file

Related-PROD: PROD-36943
Change-Id: I265058967ccc01d96bf3bca532a8a0ae2a26f1f2
diff --git a/tests/test_vm2vm_different_routers.py b/tests/test_vm2vm_different_routers.py
index 31c4478..612e5be 100644
--- a/tests/test_vm2vm_different_routers.py
+++ b/tests/test_vm2vm_different_routers.py
@@ -125,7 +125,8 @@
         for i in range(len(vms)):
             if transport1.check_vm_is_reachable_ssh(
                     floating_ip=vm_info[i]['fip'], timeout=ssh_timeout):
-                ssh.prepare_iperf(vm_info[i]['fip'], private_key=private_key)
+                ssh.IperfAtVM(
+                    vm_info[i]['fip'], private_key=private_key)
                 mtus.append(transport1.get_mtu_from_vm(
                     vm_info[i]['fip'], private_key=private_key))
         logger.info(