LU-6215 libcfs: handle topology_thread_cpumask rename

LU-6215 libcfs: handle topology_thread_cpumask rename

For linux kernel version 4.2 we see topology_thread_cpumask get
renamed in commit 06931e62246844c73fba24d7aeb4a5dc897a2739.
This patch handles this rename.

Change-Id: I7437be9a086a38762346e271b346059ccfa13a8c
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: http://review.whamcloud.com/16049
Reviewed-by: frank zago <fzago@cray.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>