[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/adapters/simulated_olt/adaptercore/simulated_olt.go b/adapters/simulated_olt/adaptercore/simulated_olt.go
index bc70a82..029f032 100644
--- a/adapters/simulated_olt/adaptercore/simulated_olt.go
+++ b/adapters/simulated_olt/adaptercore/simulated_olt.go
@@ -212,22 +212,22 @@
 	return errors.New("UnImplemented")
 }
 
-func (so *SimulatedOLT) Download_image(device *voltha.Device, request *voltha.ImageDownload)  (*voltha.ImageDownload, error) {
+func (so *SimulatedOLT) Download_image(device *voltha.Device, request *voltha.ImageDownload) (*voltha.ImageDownload, error) {
 	return nil, errors.New("UnImplemented")
 }
 
-func (so *SimulatedOLT) Get_image_download_status(device *voltha.Device, request *voltha.ImageDownload)  (*voltha.ImageDownload, error) {
+func (so *SimulatedOLT) Get_image_download_status(device *voltha.Device, request *voltha.ImageDownload) (*voltha.ImageDownload, error) {
 	return nil, errors.New("UnImplemented")
 }
 
-func (so *SimulatedOLT) Cancel_image_download(device *voltha.Device, request *voltha.ImageDownload)  (*voltha.ImageDownload, error) {
+func (so *SimulatedOLT) Cancel_image_download(device *voltha.Device, request *voltha.ImageDownload) (*voltha.ImageDownload, error) {
 	return nil, errors.New("UnImplemented")
 }
 
-func (so *SimulatedOLT) Activate_image_update(device *voltha.Device, request *voltha.ImageDownload)  (*voltha.ImageDownload, error) {
+func (so *SimulatedOLT) Activate_image_update(device *voltha.Device, request *voltha.ImageDownload) (*voltha.ImageDownload, error) {
 	return nil, errors.New("UnImplemented")
 }
 
-func (so *SimulatedOLT) Revert_image_update(device *voltha.Device, request *voltha.ImageDownload)  (*voltha.ImageDownload, error) {
+func (so *SimulatedOLT) Revert_image_update(device *voltha.Device, request *voltha.ImageDownload) (*voltha.ImageDownload, error) {
 	return nil, errors.New("UnImplemented")
 }