libext2fs: don't truncate the orphan file inode if it is newly allocated

libext2fs: don't truncate the orphan file inode if it is newly allocated

In ext2fs_create_orphan_file(), don't try truncating inode for the
orphan file if ext2fs_create_orphan_file() allocated the inode.  This
avoids problems where the newly allocated inode in the inode table
might contain garbage; if the metadata checksum feature is enabled,
this will generally result in the function failing with a checksum
invalid error, but this can cause mke2fs (which calls
ext2fs_create_orphan_file) to fail.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>