instrumentation: instrumentation for locks. (#2584)

- Instrumentation for locks.
- Detailed test coverage.
- Adding RPC control handler to fetch lock instrumentation.
- RPC control handlers suite tests with a test RPC server.

cmd/main.go

@@ -62,6 +62,9 @@ func init() {
 
 	// Set global trace flag.
 	globalTrace = os.Getenv("MINIO_TRACE") == "1"
+
+	// Set all the debug flags from ENV if any.
+	setGlobalsDebugFromEnv()
 }
 
 func migrate() {