LU-8270 ptlrpc: correct use of list_add_tail()

LU-8270 ptlrpc: correct use of list_add_tail()

In sptlrpc_gc_add_sec() swap the arguments to list_add_tail() so that
it does what we meant it to do.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: I98f4cc0cdf3e271f003c1242b36a317025974c02
Reviewed-on: http://review.whamcloud.com/20784
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>