libext2fs: handle inline_data in block iterator function

libext2fs: handle inline_data in block iterator function

After applied this commit (a7f4c635), we have banned to traverse blocks
for an inode which has inline data because no block belongs to it.  But
before calling this function, we need to check inline data flag.  This
commit add a sanity check ext2fs_inode_has_valid_blocks2() to fix them
except that ext2fs_expand_dir because it will be fixed by another patch.

Meanwhile in this commit it fixes a bug that when we kill a file we
could leak an inode.

Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>