Change GOPATH from gerrit.opencord.org to github.com/opencord

Ran `go fmt` which did some line reordering after this change

Conformed Makefile to template the imagename and use correct DOCKER_*
build variables

Change-Id: I52734e805698b305cf64eb9238b08f152f68ffd4
diff --git a/flow/flow.go b/flow/flow.go
index 8d03bb5..e86b7b7 100644
--- a/flow/flow.go
+++ b/flow/flow.go
@@ -17,8 +17,8 @@
 package flow
 
 import (
-	"gerrit.opencord.org/voltha-bbsim/common/logger"
-	openolt "gerrit.opencord.org/voltha-bbsim/protos"
+	"github.com/opencord/voltha-bbsim/common/logger"
+	openolt "github.com/opencord/voltha-bbsim/protos"
 	log "github.com/sirupsen/logrus"
 )