LU-12511 llite: fix misuse of current->parent.

LU-12511 llite: fix misuse of current->parent.

current->parent is used by ptrace to redirect some signal delivery
to the ptracer.  It should only be used by 'ptrace' or 'signal' code.
All other users should  use current->real_parent, which is the real
parent.

Change-Id: I3212fd9f3db9935b8144dba8af82eb2f387a5c45
Signed-off-by: Mr. NeilBrown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-on: https://review.whamcloud.com/45580
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>