ext4: protect journal inode's blocks using block_validity

commit 345c0dbf

 upstream.

Add the blocks which belong to the journal inode to block_validity's
system zone so attempts to deallocate or overwrite the journal due a
corrupted file system where the journal blocks are also claimed by
another inode.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=202879
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Signed-off-by: Ashwin H <ashwinh@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>