LU-6142 lustre: no need to check debugfs return values

LU-6142 lustre: no need to check debugfs return values

When calling debugfs functions, there is no need to ever check the
return value.  The function can work or not, but the code logic should
never do something different based on this.

Clean up the lustre core code by not caring about the value of debugfs
calls.  This ends up removing a number of lines of code that are not
needed.

Test-Parameters: trivial
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: I78bddd60a8ae26418e1b4f99938b21cd652aea08
Reviewed-on: https://review.whamcloud.com/37748
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>