Move singleton to common utils

Signed-off-by: Katarzyna Treder <katarzyna.treder@h-partners.com>

test_utils/common/singleton.py

@@ -0,0 +1,16 @@
+#
+# Copyright(c) 2019-2021 Intel Corporation
+# SPDX-License-Identifier: BSD-3-Clause
+#
+
+
+class Singleton(type):
+    """
+    Singleton class
+    """
+    _instances = {}
+
+    def __call__(cls, *args, **kwargs):
+        if cls not in cls._instances:
+            cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)
+        return cls._instances[cls]