Fix Geo specs failing due to "lock out" validation errors

The FactoryGirl sequence for secondary GeoNode URLs started at port 80 and
incremented after each test. When the number reached the same value as the
current node (usually port 80), the GeoNode "lock out" validation would
fail. This change starts all secondaries at a port number higher than
the current node configuration to avoid this problem entirely.

Closes #4303

spec/factories/geo_nodes.rb

 FactoryGirl.define do
   factory :geo_node do
-    sequence(:url) do |port|
+    # Start at a number higher than the current port to avoid the GeoNode
+    # "lock out" validation
+    sequence(:url, Gitlab.config.gitlab.port + 1) do |port|
       uri = URI.parse("http://#{Gitlab.config.gitlab.host}:#{Gitlab.config.gitlab.relative_url_root}")
       uri.port = port
       uri.path += '/' unless uri.path.end_with?('/')