BandwidthController - consistently use -j not --jump throughout

There's already uses of -j in places, and that's the output from
iptables-save and it's shorter.

Generated via:
  sed -i -r 's@--jump@-j@g' server/BandwidthControllerTest.cpp
  sed -i -r 's@--jump@-j@g' server/BandwidthController.cpp
Test:
  git grep '[-]-jump'   -- now comes up empty

  atest bpf_module_test clatd_test libbpf_android_test libnetdbpf_test
    netd_integration_test netd_unit_test netdutils_test
    resolv_integration_test resolv_unit_test
Bug: 136696213
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I06b8ea544f681911472c9b60336b31532c408a6f