[VOL-3005] Separate Flows from Device

Also some unit test functions moved to a test util class.
New loaders and Proxy implementation are applied.

Change-Id: Icf5a6f0a42a2dbaeff768fdb108f5e9b46644977
diff --git a/rw_core/core/device/agent_group.go b/rw_core/core/device/agent_group.go
new file mode 100644
index 0000000..18ac83a
--- /dev/null
+++ b/rw_core/core/device/agent_group.go
@@ -0,0 +1,34 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+
+ * http://www.apache.org/licenses/LICENSE-2.0
+
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package device
+
+import (
+	ofp "github.com/opencord/voltha-protos/v3/go/openflow_13"
+)
+
+// listDeviceGroups returns logical device flow groups
+func (agent *Agent) listDeviceGroups() map[uint32]*ofp.OfpGroupEntry {
+	groupIDs := agent.groupLoader.List()
+	groups := make(map[uint32]*ofp.OfpGroupEntry, len(groupIDs))
+	for groupID := range groupIDs {
+		if groupHandle, have := agent.groupLoader.Lock(groupID); have {
+			groups[groupID] = groupHandle.GetReadOnly()
+			groupHandle.Unlock()
+		}
+	}
+	return groups
+}