Geo: Do not fail current_node recognition when name is missing a slash

What does this MR do and why?

Currently, each time the name field on GeoNode is updated, we check if the new value + a trailing slash matches the url. If it does, before saving, we add the slash to the DB value.

However, this behaviour causes a bug in the case where a user consciously uses the site's URL without a slash for the node name.

To silently remove this bug, I've done the following:

1. Remove the automatic slash addition to the default setting. Now if gitlab_rails['node_name'] is empty, the default value is the URL, un-changed.
2. Remove the name and name= methods from GeoNode. This guarantees that GeoNode.name always returns the database value and saves the name unchanged.
3. Add complex logic to GeoNode.current_node and GeoNode.current?(node) to catch all corner cases concerning trailing slashes.

The last point logic can be defined as follows:

• First we check if the value matches. If they do, very well! We've got our node. Else, we need to see if we fall under a corner case.
• The corner case only happens when the name resembles the url. So we make sure that .current_node checks when the current_node_name matches the current_node_url with or without a trailing slash. Similarly, for .current?(node) we check that the node.name and node.url match with or without trailing slashes.
• If the name and the URL don't match even with/without a trailing slash, the node isn't found.

References

Relates to: #536444 (closed)

How to set up and validate locally

• On a Geo-enabled GDK, open config/gitlab.yml and the Rails console.
• Play around various values of geo: node_name: in the config and GeoNode.current_node.name in the Rails console.
• You can find a table of values I've tested on in my primary GDK in this spreadsheet, under the "Fix: tested values" tab.

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