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/grpc_service.go b/core/grpc_service.go
index a33e21c..8e9e122 100644
--- a/core/grpc_service.go
+++ b/core/grpc_service.go
@@ -19,13 +19,13 @@
 import (
 	"net"
 
-	"gerrit.opencord.org/voltha-bbsim/common/logger"
-	"gerrit.opencord.org/voltha-bbsim/device"
-	flowHandler "gerrit.opencord.org/voltha-bbsim/flow"
-	openolt "gerrit.opencord.org/voltha-bbsim/protos"
 	"github.com/google/gopacket"
 	"github.com/google/gopacket/layers"
 	omci "github.com/opencord/omci-sim"
+	"github.com/opencord/voltha-bbsim/common/logger"
+	"github.com/opencord/voltha-bbsim/device"
+	flowHandler "github.com/opencord/voltha-bbsim/flow"
+	openolt "github.com/opencord/voltha-bbsim/protos"
 	log "github.com/sirupsen/logrus"
 	"golang.org/x/net/context"
 	"google.golang.org/grpc"