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/core/omci.go b/core/omci.go
index 2566f2a..b0e6bbb 100644
--- a/core/omci.go
+++ b/core/omci.go
@@ -19,9 +19,9 @@
 import (
 	"context"
 
-	"gerrit.opencord.org/voltha-bbsim/common/logger"
-	openolt "gerrit.opencord.org/voltha-bbsim/protos"
 	omci "github.com/opencord/omci-sim"
+	"github.com/opencord/voltha-bbsim/common/logger"
+	openolt "github.com/opencord/voltha-bbsim/protos"
 )
 
 // RunOmciResponder starts a go routine to process/respond to OMCI messages from VOLTHA