Unable to run Elasticsearch with single-node discovery setting.

[franciszabala]

Describe the feature:

Elasticsearch version: 5.1.1

Plugins installed: vanilla install

JVM version (java -version): 1.8.0_131

OS version (uname -a if on a Unix-like system): Ubuntu 16.04

Description of the problem including expected versus actual behavior: Unable to run Elasticsearch using "single-node"

Steps to reproduce:

Please include a minimal but complete recreation of the problem, including
(e.g.) index creation, mappings, settings, query etc. The easier you make for
us to reproduce it, the more likely that somebody will take the time to look at it.

1. Download and extract Elasticsearch 5.1.1
2. add discovery.type: single-node to config/elasticsearch.yml
3. set network.host: site

Provide logs (if relevant):

Caused by: java.lang.IllegalArgumentException: Unknown discovery type [single-node]
at org.elasticsearch.discovery.DiscoveryModule.(DiscoveryModule.java:93) ~[elasticsearch-5.1.1.jar:5.1.1]

[tvernum]

Single node discovery was introduced in Elasticsearch 5.4, it will not work in 5.1.1

If there is documentation somewhere that suggests this will work, please let us know so we can fix it.

I'm going to close this issue, as it is not a bug.