Add note to collect CONSUL_SERVER_NODES in HA docs

There are several instances in our HA docs where an example of
`Y.Y.Y.Y consul1.gitlab.example.com Z.Z.Z.Z` is given,
but this value isn't explicitly stated. It should be
the IP addresses or DNS records of the Consul server nodes.

doc/administration/high_availability/gitaly.md

@@ -24,6 +24,8 @@ Continue configuration of other components by going back to:
 
 > [Introduced](https://gitlab.com/gitlab-org/omnibus-gitlab/issues/3786) in GitLab 12.0.
 
+1. Make sure to collect [`CONSUL_SERVER_NODES`](database.md#consul-information), which are the IP addresses or DNS records of the Consul server nodes, for the next step. Note they are presented as `Y.Y.Y.Y consul1.gitlab.example.com Z.Z.Z.Z`
+
 1. Create/edit `/etc/gitlab/gitlab.rb` and add the following configuration:
 
    ```ruby

doc/administration/high_availability/gitlab.md

@@ -138,6 +138,8 @@ need some extra configuration.
 
 If you enable Monitoring, it must be enabled on **all** GitLab servers.
 
+1. Make sure to collect [`CONSUL_SERVER_NODES`](database.md#consul-information), which are the IP addresses or DNS records of the Consul server nodes, for the next step. Note they are presented as `Y.Y.Y.Y consul1.gitlab.example.com Z.Z.Z.Z`
+
 1. Create/edit `/etc/gitlab/gitlab.rb` and add the following configuration:
 
    ```ruby

doc/administration/high_availability/monitoring_node.md

@@ -16,6 +16,8 @@ Omnibus:
    package you want using **steps 1 and 2** from the GitLab downloads page.
    - Do not complete any other steps on the download page.
 
+1. Make sure to collect [`CONSUL_SERVER_NODES`](database.md#consul-information), which are the IP addresses or DNS records of the Consul server nodes, for the next step. Note they are presented as `Y.Y.Y.Y consul1.gitlab.example.com Z.Z.Z.Z`
+
 1. Edit `/etc/gitlab/gitlab.rb` and add the contents:
 
     ```ruby

doc/administration/high_availability/redis.md

@@ -756,6 +756,8 @@ gitlab_rails['redis_sentinels'] = [
 
 If you enable Monitoring, it must be enabled on **all** Redis servers.
 
+1. Make sure to collect [`CONSUL_SERVER_NODES`](database.md#consul-information), which are the IP addresses or DNS records of the Consul server nodes, for the next step. Note they are presented as `Y.Y.Y.Y consul1.gitlab.example.com Z.Z.Z.Z`
+
 1. Create/edit `/etc/gitlab/gitlab.rb` and add the following configuration:
 
    ```ruby