#560 - Fix server config validation issues.

Fixes:

1. Test Email functionality in server configuration page.
2. Validate LDAP functionality in server configuration page.
3. Reload Command Repo Cache functionality in server configuration page.

All were broken because CSRF token was not being sent, and in Rails 4, even
AJAX requests are checked for CSRF. Wasn't the case with Rails 2.
How about adding a ```<%= form_tag -%>``` around the button, so that Rails generates the auth token automatically , passing in the ```form``` element into JS and using 
```javascript
jQuery.post({... 
  data: form.serialize(),
...});
```
 instead?

From ```request_forgery_protection.rb```, 
```ruby
    def verified_request?
        !protect_against_forgery? || request.get? || request.head? ||
          form_authenticity_token == params[request_forgery_protection_token] ||
          form_authenticity_token == request.headers['X-CSRF-Token']
      end

      # Sets the token value for the current session.
      def form_authenticity_token
        session[:_csrf_token] ||= SecureRandom.base64(32)
      end
```

we could potentially short-circuit a valid call @ ```form_authenticity_token == params[request_forgery_protection_token]``` rather than calling ```form_authenticity_token``` twice which means reading the session twice.

If you think it isn't that big of a deal, I'm ok with the current implementation.