make failing to start TrafficController critical.

I don't want to debug any more kernel regressions, like the one
introduced by "bpf: program: Refuse non-O_RDWR flags in BPF_OBJ_GET":
  06-18 07:35:36.014   360   360 E TrafficController: Failed to get program from /sys/fs/bpf/prog_netd_cgroupskb_egress_stats: Invalid argument
  06-18 07:35:36.023   360   360 E netd    : Failed to start trafficcontroller: (Status[code: 22, msg: "[Invalid argument] : cgroup program get failed"])
which fail to get caught and cause failures in bpf_module_test
(the test seems to get run very unreliably, people will much more
easily notice device simply failing to boot due to netd/systemserver
crash looping).

see also:
  https://android-review.googlesource.com/c/kernel/common/+/1738604
  https://android-review.googlesource.com/c/kernel/common/+/1741194
  https://patchwork.kernel.org/project/netdevbpf/patch/20210618105526.265003-1-zenczykowski@gmail.com/



Test: atest
Bug: 191826861
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Original-Change: https://android-review.googlesource.com/1740456
Merged-In: If87f02ea6fb713ebbb9a98dbc6c9b6ac477b727e
Change-Id: If87f02ea6fb713ebbb9a98dbc6c9b6ac477b727e