ext4: remove calls to ext4_jbd2_file_inode() from delalloc write path

The calls to ext4_jbd2_file_inode() are needed to guarantee that we do
not expose stale data in the data=ordered mode.  However, they are not
necessary because in all of the cases where we have newly allocated
blocks in the delayed allocation write path, we immediately submit the
dirty pages for I/O.  Hence, we can avoid the overhead of adding the
inode to the list of inodes whose data pages will be to be flushed out
to disk completely during the next commit operation.

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