fix: Solve the problem of program entering umount loop caused by some file has...

fix: Solve the problem of program entering umount loop caused by some file has +i or +a attribute that cann't delete.

After some deb packages are installed, some +i or +a files will be created in the file system to prevent them from being deleted by mistake; but after these packages are installed in the environment created by pbuilder, will cause umount loop when exiting. Signed-off-by: xinpeng wang wangxinpeng@uniontech.com