[VOL-1588] Improve Flow Add performance

This update consists of the following:
1) Update the performance when adding a flow to a logical device,
decomposing the flow into parent and child device and sending the
flow to the adapters.
2) Format a number of files as per GO fmt.
3) Ensure the device graph cache gets updated when a new port is
added to the graph that belongs to an existing device in cache.

The flow update/deletion performance will be addressed in a separate
commit.

Change-Id: I2eb663cc73eef9fc6172203ed88a35726f5fe008
diff --git a/rw_core/core/adapter_manager.go b/rw_core/core/adapter_manager.go
index 07a4826..5d539aa 100644
--- a/rw_core/core/adapter_manager.go
+++ b/rw_core/core/adapter_manager.go
@@ -164,7 +164,7 @@
 	} else {
 		log.Debug("no-existing-device-type-found")
 		//	No device types data.   In order to have a proxy setup for that path let's create a fake device type
-		aMgr.addDeviceTypes(&voltha.DeviceTypes{Items: []*voltha.DeviceType{&voltha.DeviceType{Id: SENTINEL_DEVICETYPE_ID, Adapter: SENTINEL_ADAPTER_ID}}}, true)
+		aMgr.addDeviceTypes(&voltha.DeviceTypes{Items: []*voltha.DeviceType{{Id: SENTINEL_DEVICETYPE_ID, Adapter: SENTINEL_ADAPTER_ID}}}, true)
 	}
 }