Free pidfile_path atexit()

To prevent warnings from tools like Valgrind, or handle issues
with RAM leaks on non-MMU systems like uClinux, we must free
the memory allocated by pidfile().

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

pidfile.c

@@ -122,8 +122,10 @@ pidfile(const char *basename)
 static void
 pidfile_cleanup(void)
 {
-
-	if (pidfile_path != NULL && pidfile_pid == getpid())
+	if (pidfile_path != NULL && pidfile_pid == getpid()) {
 		(void) unlink(pidfile_path);
+		free(pidfile_path);
+		pidfile_path = NULL;
+	}
 }
 #endif