nfsd: Clone should commit src file metadata too

vfs_clone_file_range() can modify the metadata on the source file too,
so we need to commit that to stable storage as well.

Reported-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Acked-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>