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/bbsim.go b/bbsim.go
index dd68b82..34a61c5 100644
--- a/bbsim.go
+++ b/bbsim.go
@@ -19,8 +19,8 @@
 import (
 	"log"
 
-	"gerrit.opencord.org/voltha-bbsim/common/logger"
-	"gerrit.opencord.org/voltha-bbsim/core"
+	"github.com/opencord/voltha-bbsim/common/logger"
+	"github.com/opencord/voltha-bbsim/core"
 )
 
 func printBanner() {