Test improvements that were affecting enterprise test scenarios

- Remove hardcoding of disabling districts for
  broker/test/functional_ext/removed_nodes_app_fixup_test.rb

- Delete test user on teardown for
  admin-console/test/functional/admin_console/api/search/users_controller_test.rb

- Remove the not-enterprise tag from
  controller/test/cucumber/runtime-cartridge-mongodb.feature