Log Message:
Update sysutils/consul to 0.7.3.

FEATURES:

- KV Import/Export CLI: consul kv export and consul kv import can be
  used to move parts of the KV tree between disconnected consul
  clusters, using JSON as the intermediate representation.
- Node Metadata: Support for assigning user-defined metadata key/value
  pairs to nodes has been added.
- Node Identifiers: Consul agents can now be configured with a unique
  identifier, or they will generate one at startup that will persist
  across agent restarts.
- Improved Blocking Queries: Consul's blocking query implementation was
  improved to provide a much more fine-grained mechanism for detecting
  changes.
- GCE auto-discovery: New -retry-join-gce configuration options added to
  allow bootstrapping by automatically discovering Google Cloud
  instances with a given tag at startup.

IMPROVEMENTS:

- build: Consul is now built with Go 1.7.4.
- cli: consul kv get now has a -base64 flag to base 64 encode the value.
- cli: consul kv put now has a -base64 flag for setting values which are
  base 64 encoded.
- ui: Added a notice that JS is required when viewing the web UI with JS
  disabled.

BUG FIXES:

- agent: Redacted the AWS access key and secret key ID from the
  /v1/agent/self output so they are not disclosed.
- agent: Fixed a rare startup panic due to a Raft/Serf race condition.
- cli: Fixed a panic when an empty quoted argument was given to consul
  kv put.
- tests: Fixed a race condition with check mock's map usage.