Fix context depending on connected?

For some reason I can't get our connected? to return true. It's unclear
whether its a (monkey patching) bug in our app, but it shouldn't be
necessary here anyways since we're only looking at statically defined
configuration.

This rescue may not be necessary, there's one test in Rails' suite that
fails without it but it seems suspect.

Author: skipkayhil

activerecord/lib/active_record/model_schema.rb

@@ -205,9 +205,8 @@ module ClassMethods
       # Returns the current schema context key from the connection configuration.
       # Defaults to "default" if no connection is available or no context is configured.
       def current_schema_context_key # :nodoc:
-        return "default" unless connected?
         connection_db_config.schema_context_key
-      rescue
+      rescue ConnectionNotDefined
         "default"
       end