Log Message:
Update sysutils/consul to 0.8.1.

IMPROVEMENTS:
- agent: Node IDs derived from host information are now hashed to
  prevent things like common server hardware from generating IDs with
  a common prefix across nodes.
- agent: Added new -disable-host-node-id CLI flag and
  disable_host_node_id config option to the Consul agent to prevent it
  from using information from the host when generating a node ID.
- agent: Removed useless "==> Caught signal: broken pipe" logging
  since that often results from problems sending telemetry or broken
  incoming client connections; operators don't need to be alerted to
  these.
- cli: Added TLS options for setting the client/CA certificates to use
  when communicating with Consul.
- build: Consul is now built with Go 1.8.1.
- ui: Updates Consul assets to new branding.

BUG FIXES:
- api: Added missing Raft index fields to AgentService and Node
  structures.
- server: Fixed an issue where flood joins would not work with IPv6
  addresses.
- server: Fixed an issue where electing a 0.8.x leader during an
  upgrade would cause a panic in older servers.
- server: Fixed an issue where tracking of leadership changes could
  become incorrect when changes occurred very rapidly.
- server: Fixed a panic when checking ACLs on a session that doesn't
  exist.