PLT-6080 moving clustering to memberlist (#6499)

* PLT-6080 adding cluster discovery service

* Adding memberlist lib

* Adding memberlist lib

* WIP

* WIP

* WIP

* WIP

* Rolling back config changes

* Fixing make file

* Fixing config for cluster

* WIP

* Fixing system console for clustering

* Fixing default config

* Fixing config

* Fixing system console for clustering

* Tweaking hub setting

* Bumping up time

* merging vendor dir

* Updating vendor dir

* Fixing unit test

* Fixing bad merge

* Remove some testing code

* Moving comment

* PLT-6868 adding db ping retry

* Removing unused loc strings

* Adding defer to cancel

webapp/i18n/en.json

@@ -157,14 +157,14 @@
   "admin.cluster.interNodeUrlsEx": "E.g.: \"http://10.10.10.30, http://10.10.10.31\"",
   "admin.cluster.interNodeUrlsTitle": "Inter-Node URLs:",
   "admin.cluster.loadedFrom": "This configuration file was loaded from Node ID {clusterId}. Please see the Troubleshooting Guide in our <a href=\"http://docs.mattermost.com/deployment/cluster.html\" target='_blank'>documentation</a> if you are accessing the System Console through a load balancer and experiencing issues.",
-  "admin.cluster.noteDescription": "Changing properties in this section will require a server restart before taking effect. When High Availability mode is enabled, the System Console is set to read-only and can only be changed from the configuration file.",
+  "admin.cluster.noteDescription": "Changing properties in this section will require a server restart before taking effect. When High Availability mode is enabled, the System Console is set to read-only and can only be changed from the configuration file unless ReadOnlyConfig is disabled in the configuration file.",
   "admin.cluster.should_not_change": "WARNING: These settings may not sync with the other servers in the cluster. High Availability inter-node communication will not start until you modify the config.json to be identical on all servers and restart Mattermost. Please see the <a href=\"http://docs.mattermost.com/deployment/cluster.html\" target='_blank'>documentation</a> on how to add or remove a server from the cluster. If you are accessing the System Console through a load balancer and experiencing issues, please see the Troubleshooting Guide in our <a href=\"http://docs.mattermost.com/deployment/cluster.html\" target='_blank'>documentation</a>.",
   "admin.cluster.status_table.config_hash": "Config File MD5",
   "admin.cluster.status_table.hostname": "Hostname",
   "admin.cluster.status_table.id": "Node ID",
   "admin.cluster.status_table.reload": " Reload Cluster Status",
   "admin.cluster.status_table.status": "Status",
-  "admin.cluster.status_table.url": "Inter-Node URL",
+  "admin.cluster.status_table.url": "Gossip Address",
   "admin.cluster.status_table.version": "Version",
   "admin.cluster.unknown": "unknown",
   "admin.compliance.directoryDescription": "Directory to which compliance reports are written. If blank, will be set to ./data/.",