Add fix for upgrade galera with mysql 5.7

--add update-mysql-version parametr for major upgrade

Related-Prod: PROD-36708
Change-Id: Ic1eb785c7f42a7532f55946aa6c024430810e0bf
diff --git a/tcp_tests/tests/system/conftest.py b/tcp_tests/tests/system/conftest.py
index 0dabd4d..74b3ea3 100644
--- a/tcp_tests/tests/system/conftest.py
+++ b/tcp_tests/tests/system/conftest.py
@@ -84,6 +84,7 @@
 
 def pytest_addoption(parser):
     parser.addoption("--update-to-tag",
+                     "--update-mysql-version",
                      action="store",
                      default=None,
                      help="For mcp_update test")