[27450] Fixed the issue with the Boost UDP resolver overriding the
default DNS server list for vRouter using the etc/resolve.conf file
on a dedicated OpenStack compute node. Now, using the new
resolv_conf_file option, you can specify a file
that contains a list of DNS nameserver that contrail-vrouter-agent
will use as a non-default source of custom nameservers. For details,
see: MCP Operations Guide: Override the default DNS server
list for vRouter.