libext2fs: write only core inode in update_path()

libext2fs: write only core inode in update_path()

The ext2_extent_handle only has a struct ext2_inode allocated on
it, and the same amount copied into it in that same function,
but in update_path() we're possibly writing out more than that -
for example 256 bytes, from that address.  This causes uninitialized
memory to get  written to disk, overwriting the parts of the
inode past the osd2 member (the end of the smaller structure).

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>