fix(grpc): Fixes issue where message sending limited to 4mb

Between grpc 1.2.x and 1.7.x there was an API change. The
previous MaxMsgSize is now a wrapper around MaxRecvMsgSize. This
change now sets the MaxRecvMsgSize and MaxSendMsgSize which need
to be set independently.

(cherry picked from commit 614cd9dfe7)

pkg/tiller/server.go

@@ -36,7 +36,8 @@ var maxMsgSize = 1024 * 1024 * 20
 // DefaultServerOpts returns the set of default grpc ServerOption's that Tiller requires.
 func DefaultServerOpts() []grpc.ServerOption {
 	return []grpc.ServerOption{
-		grpc.MaxMsgSize(maxMsgSize),
+		grpc.MaxRecvMsgSize(maxMsgSize),
+		grpc.MaxSendMsgSize(maxMsgSize),
 		grpc.UnaryInterceptor(newUnaryInterceptor()),
 		grpc.StreamInterceptor(newStreamInterceptor()),
 	}