Show clear message when set-geo-primary-node was successful

Closes gitlab-org/gitlab-ee#2177.

changelogs/unreleased-ee/tc-geo-set_primary_node-success.yml

+---
+title: Show clear message when set-geo-primary-node was successful
+merge_request: 3768
+author:
+type: changed

ee/lib/gitlab/geo/geo_tasks.rb

@@ -5,10 +5,14 @@ module Gitlab
 
       def set_primary_geo_node
         node = GeoNode.new(primary: true, url: GeoNode.current_node_url)
-        $stdout.puts "Saving primary GeoNode with URL #{node.url}".color(:green)
+        $stdout.puts "Saving primary Geo node with URL #{node.url} ..."
         node.save
 
-        $stdout.puts "Error saving GeoNode:\n#{node.errors.full_messages.join("\n")}".color(:red) unless node.persisted?
+        if node.persisted?
+          $stdout.puts "#{node.url} is now the primary Geo node".color(:green)
+        else
+          $stdout.puts "Error saving Geo node:\n#{node.errors.full_messages.join("\n")}".color(:red)
+        end
       end
 
       def refresh_foreign_tables!

spec/ee/spec/lib/gitlab/geo/geo_tasks_spec.rb

+require 'spec_helper'
+
+describe Gitlab::Geo::GeoTasks do
+  describe '.set_primary_geo_node' do
+    before do
+      allow(GeoNode).to receive(:current_node_url).and_return('https://primary.geo.example.com')
+    end
+
+    it 'sets the primary node' do
+      expect { subject.set_primary_geo_node }.to output(/https:\/\/primary.geo.example.com\/ is now the primary Geo node/).to_stdout
+    end
+
+    it 'returns error when there is already a Primary node' do
+      create(:geo_node, :primary)
+
+      expect { subject.set_primary_geo_node }.to output(/Error saving Geo node:/).to_stdout
+    end
+  end
+end