LU-8066 obd: make ldebugfs_remove recursive

LU-8066 obd: make ldebugfs_remove recursive

ldebugfs_remove is usually called on directories with files passed in
as attributes, so simple debugfs_remove failes on them as not empty
Switch to debugfs_remove_recursive.

This fixes a number of problems where a new filesystem is mounted after
being unmounted first.

Linux-commit: 6a491f2b80f2806221ba3a5a3e26fbe945f82d83

Change-Id: I49878ea9e28365d7d834497e715eeee21e698eea
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/28818
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>