filter_seccomp: skip seccomp setup when there's nothing to filter

filter_seccomp: skip seccomp setup when there's nothing to filter

If the trace_set set is complete (no syscalls are filtered), seccomp
filtering is disabled.  This patch adds a new is_complete_set_array
function to check whether all sets of a set array are complete.

* number_set.c (is_complete_set_array): New function.
* number_set.h (is_complete_set_array): New prototype.
* filter_seccomp.c (check_seccomp_filter): Skip seccomp setup if there is
nothing to filter.

Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>