parasite: Declare @tid as pid_t in parasite_dump_thread

Just to be consistent with types we're using.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/parasite.h

@@ -95,7 +95,7 @@ struct parasite_dump_creds {
 
 struct parasite_dump_thread {
 	unsigned int		*tid_addr;
-	int			tid;
+	pid_t			tid;
 };
 
 #define PARASITE_MAX_FDS	(PAGE_SIZE / sizeof(int))