Fix method full name generation

Signed-off-by: Kevin Parsons <kevpar@microsoft.com>

services.go

@@ -152,5 +152,5 @@ func convertCode(err error) codes.Code {
 }
 
 func fullPath(service, method string) string {
-	return "/" + path.Join("/", service, method)
+	return "/" + path.Join(service, method)
 }

services_test.go

@@ -0,0 +1,29 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package ttrpc
+
+import (
+	"testing"
+)
+
+func Test_MethodFullNameGeneration(t *testing.T) {
+	name := fullPath("test.v1.service", "Foo")
+	expectedName := "/test.v1.service/Foo"
+	if name != expectedName {
+		t.Fatalf("Service name does not match. Expected: %q, Actual: %q", expectedName, name)
+	}
+}