LU-11062 libcfs: use save_stack_trace for stack dump

LU-11062 libcfs: use save_stack_trace for stack dump

The stacktrace_ops has been removed recently. So we
have to use save_stack_trace_tsk for stack trace
dump.

Lustre-change: https://review.whamcloud.com/#/c/32952/
Lustre-commit: 574e63fc86553510d87d02cd6d72785f341e48dc

Test-Parameters: trivial
Signed-off-by: Yang Sheng <ys@whamcloud.com>
Change-Id: Icb3d0dbd62c35fdd9b8de925aec9358a2208814f
Reviewed-on: https://review.whamcloud.com/32972
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <jhammond@whamcloud.com>