net-test: require ANDROID_PARANOID_NETWORK to be turned off

This functionality is long deprecated and has now (for a while)
been implemented via eBPF.  It's best to be consistent
about security features.

Note that unlike what one could expect from the name,
ANDROID_PARANOID_NETWORK actually mostly grants *more* privs
rather than reducing them, it:
  (a) requires CAP_NET_ADMIN for all tun char device ioctl != TUNGETIFF
      (even TUNGETFEATURES!!!)
  (b) automatically grants CAP_NET_RAW to AID_NET_RAW group
  (c) automatically grants CAP_NET_ADMIN to AID_NET_ADMIN group.

ACK 4.14-r already has this reverted out of the kernel tree.

ACK 4.14-q has this default enabled, but it's covered by a Kconfig
option (CONFIG_ANDROID_PARANOID_NETWORK) and can thus be trivially
turned off.

Additionally devices updating to U will probably have
switched from 4.14-q to 4.14-r based kernels anyway.

Test: TreeHugger, manually on UML with
  unmodified ACK 4.14-R
  and on ACK 4.14-Q with ANDROID_PARANOID_NETWORK default y->n
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I32794f0cac00585f781f9668f8c2c333d2f83fa5