Changes

testenv: podman: disable send_redirects

When starting podman, set the following sysctls to avoid ICMP redirects.
ICMP redirects lead to test failures (TC_pdp4_clients_interact in the
GGSN testsuite), and should not be sent in the test environment in
general.

  net.ipv4.conf.all.send_redirects=0
  net.ipv4.conf.default.send_redirects=0

It is really needed to set both "all" and "default", or otherwise ICMP
redirects still show up. I've seen setting both in this patch:
https://patchwork.kernel.org/project/linux-kselftest/patch/1570719055-25110-4-git-send-email-yanhaishuang@cmss.chinamobile.com/

Fixes: OS#6575
Change-Id: Ie27668f38b80c52ffef4e17b3fe64f0c9109bdea