This quells a warning about "Option environment must be a kind of
[String]" that gets emitted during rspec runs. Chef 13 will not allow
the type mismatch.

The consul_service resource was using a default value attribute that was
not configured anywhere. This changes it to use the same default as
consul_config.

On my system, this fixes the following failures under Centos 5:

 1) Service "consul" should be enabled
    Failure/Error: it { should be_enabled }
      expected Service "consul" to be enabled
      /bin/sh -c chkconfig\ --list\ consul\ \|\ grep\ 3:on

    # /tmp/verifier/suites/serverspec/default_spec.rb:26:in `block (2 levels) in <top (required)>'

 2) Service "consul" should be running
    Failure/Error: it { should be_running }
      expected Service "consul" to be running
      /bin/sh -c service\ consul\ status

    # /tmp/verifier/suites/serverspec/default_spec.rb:27:in `block (2 levels) in <top (required)>'