vendor: add qingstor-sdk-go for QingStor

vendor/github.com/pengsrc/go-shared/pid/pidfile_darwin.go

@@ -0,0 +1,14 @@
+// +build darwin
+
+package pid
+
+import (
+	"syscall"
+)
+
+func processExists(pid int) bool {
+	// OS X does not have a proc filesystem.
+	// Use kill -0 pid to judge if the process exists.
+	err := syscall.Kill(pid, 0)
+	return err == nil
+}