VOL-1497 : Add more control to kv/memory access

- Added kv locking mechanism (etcd only)
- (watch) control path access whenever possible
- (watch) use a transaction for updates and merge with memory
- cleaned up vendoring
- misc changes to fix exceptions found along the way

Amendments:

- Copyright header got removed in auto-generated file
- Changed default locking to false for KV list operation
- Updated backend api to allow the passing of locking parameter

Change-Id: Ie1a55d3ca8b9d92ae71a85ce42bb22fcf1419e2c
diff --git a/vendor/google.golang.org/grpc/balancer/balancer.go b/vendor/google.golang.org/grpc/balancer/balancer.go
index 1bf46aa..317c2e7 100644
--- a/vendor/google.golang.org/grpc/balancer/balancer.go
+++ b/vendor/google.golang.org/grpc/balancer/balancer.go
@@ -28,6 +28,7 @@
 
 	"google.golang.org/grpc/connectivity"
 	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/internal"
 	"google.golang.org/grpc/metadata"
 	"google.golang.org/grpc/resolver"
 )
@@ -47,6 +48,18 @@
 	m[strings.ToLower(b.Name())] = b
 }
 
+// unregisterForTesting deletes the balancer with the given name from the
+// balancer map.
+//
+// This function is not thread-safe.
+func unregisterForTesting(name string) {
+	delete(m, name)
+}
+
+func init() {
+	internal.BalancerUnregister = unregisterForTesting
+}
+
 // Get returns the resolver builder registered with the given name.
 // Note that the compare is done in a case-insenstive fashion.
 // If no builder is register with the name, nil will be returned.