Sysctl was missing from the linuxbridge plugin rootwrap
configuration file. This was causing failures in the
linuxbridge agent when networks are created:
Rootwrap error running command: ['sysctl', '-w', 'net.ipv6.conf.eth0/557.disable_ipv6=1']:
NOTE: this bug was hidden by the fact that sysctl was
covered by the iptables-firewall.filters until recently,
when it was removed (see https://review.openstack.org/#/c/436315/).
Change-Id: Id20175df30d4d6039fb42e722d03f39521f6a499
Closes-Bug: #1715194