hfsplus: fix issue with unzeroed unused b-tree nodes

The fsck_hfs (under MacOS X) complains about unzeroed unused b-tree nodes
after deletion of folders' tree under Linux.

SYMPTOMS:

  Running Disk Utiltiy's "Verify Disk" on "test" gives the following:
  Verifying volume “Test”
  Checking file systemChecking Journaled HFS Plus volume.
  Checking extents overflow file.
  Checking catalog file.
  Unused node is not erased (node = 3111)
  Checking multi-linked files.
  Checking catalog hierarchy.
  Checking extended attributes file.
  Checking volume bitmap.
  Checking volume information.
  The volume Test was found corrupt and needs to be repaired.
  Error: This disk needs to be repaired. Click Repair Disk.

REPRODUCING PATH:

1. Prepare HFS+ (non-case sensitive) partition (for example, 5GB)
   under MacOS X.
2. Copy linux kernel source tree (for example, 3.7-rc6 version) on
   this partition under MacOS X.
3. Then switch to Linux and mount this prepared partition.
4. Execute `sudo rm -r` under prepared directory with linux kernel
   source tree.
5. Unmount and boot back into OS X.
6. Open up Disk Utility and verify partition.

REPRODUCIBILITY: 100%

FIX:

It is added code of node clearing in hfs_bnode_put() method for the case
when node has flag HFS_BNODE_DELETED.

Signed-off-by: Vyacheslav Dubeyko <slava@dubeyko.com>
Reported-by: Kyle Laracey <kalaracey@gmail.com>
Acked-by: Hin-Tak Leung <htl10@users.sourceforge.net>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>