[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/transaction.go b/rw_core/core/transaction.go
index 12bf93e..711f3b5 100644
--- a/rw_core/core/transaction.go
+++ b/rw_core/core/transaction.go
@@ -35,7 +35,7 @@
 package core
 
 import (
-	log "github.com/opencord/voltha-go/common/log"
+	"github.com/opencord/voltha-go/common/log"
 	"github.com/opencord/voltha-go/db/kvstore"
 	"time"
 )