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/api_handler.go b/core/api_handler.go
index eb52977..d6c051a 100644
--- a/core/api_handler.go
+++ b/core/api_handler.go
@@ -22,9 +22,9 @@
 	"strconv"
 	"time"
 
-	pb "gerrit.opencord.org/voltha-bbsim/api"
-	"gerrit.opencord.org/voltha-bbsim/common/logger"
-	"gerrit.opencord.org/voltha-bbsim/device"
+	pb "github.com/opencord/voltha-bbsim/api"
+	"github.com/opencord/voltha-bbsim/common/logger"
+	"github.com/opencord/voltha-bbsim/device"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
 )