Ignore traffic from cache-local SSL terminators

Since

  https://gerrit.wikimedia.org/r/#/c/175465/

all caches (not only ulsfo's caches) come with their own SSL
terminator. So we ignore requests from the subnets of the caches to
not count SSL requests twice.

This change will slow down filter by ~5%. But as the filter process is
running at <20% utilization of a CPU after fixing the compiler
optimization flag, the additional ~5% should be fine.

Also this change stops counting some monitoring requests (which seems
fair), and also has some few false negatives, as not counting requests
from xenon.

Bug: T76390
Change-Id: Ic6e1f8e6f58091b2274a3ab45ddfe38bc9489591