VOL-1460 Updated core to use voltha-protos instead of local protos
Moved protos to python directory in order to maintain functionaly of containers built there.
Added capability to do local builds of protos
Added instructions on running dep ensure for getting protos.
Updated github.com/golang/protobuf version to v1.3.1

Change-Id: Ia6ef55f07f0d5dcb5b750d7c37b21b71db85bfc4
diff --git a/vendor/google.golang.org/grpc/internal/internal.go b/vendor/google.golang.org/grpc/internal/internal.go
index eaa54d4..c1d2c69 100644
--- a/vendor/google.golang.org/grpc/internal/internal.go
+++ b/vendor/google.golang.org/grpc/internal/internal.go
@@ -20,11 +20,12 @@
 // symbols to avoid circular dependencies.
 package internal
 
-import "context"
+import (
+	"context"
+	"time"
+)
 
 var (
-	// WithContextDialer is exported by dialoptions.go
-	WithContextDialer interface{} // func(context.Context, string) (net.Conn, error) grpc.DialOption
 	// WithResolverBuilder is exported by dialoptions.go
 	WithResolverBuilder interface{} // func (resolver.Builder) grpc.DialOption
 	// WithHealthCheckFunc is not exported by dialoptions.go
@@ -33,6 +34,9 @@
 	HealthCheckFunc HealthChecker
 	// BalancerUnregister is exported by package balancer to unregister a balancer.
 	BalancerUnregister func(name string)
+	// KeepaliveMinPingTime is the minimum ping interval.  This must be 10s by
+	// default, but tests may wish to set it lower for convenience.
+	KeepaliveMinPingTime = 10 * time.Second
 )
 
 // HealthChecker defines the signature of the client-side LB channel health checking function.