Revert "nfs: take extra reference to fl->fl_file when running a LOCKU operation"

Revert "nfs: take extra reference to fl->fl_file when running a LOCKU operation"

This reverts commit 6bd60992ec8b9ddf216f13d3e6788f4871b04c4c.

William reported that he was seeing instability with this patch, which
is likely due to the fact that it can cause the kernel to take a new
reference to a filp after the last reference has already been put.

Revert this patch for now, as we'll need to fix this in another way.

Cc: stable@vger.kernel.org
Reported-by: William Dauchy <william@gandi.net>
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Reviewed-by: "J. Bruce Fields" <bfields@fieldses.org>
Tested-by: "J. Bruce Fields" <bfields@fieldses.org>