Update series metadata

Ensure that EOL releases are removed from metadata
and tests, and that the current dev release is enabled
in metadata.  Dev release tests are enabled separately
because of chickens and eggs.

Change-Id: I1e0b7d0d0994fd229c15cf8c456b2b82bc4041e8

metadata.yaml

@@ -12,7 +12,7 @@ extra-bindings:
 series:
   - xenial
   - bionic
-  - artful
+  - cosmic
   - trusty
 provides:
   nrpe-external-master:

tests/gate-basic-artful-pike

@@ -1,26 +0,0 @@
-#!/usr/bin/env python
-#
-# Copyright 2016 Canonical Ltd
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#  http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-"""Amulet tests on a basic openstack-dashboard deployment on artful-pike."""
-
-from basic_deployment import OpenstackDashboardBasicDeployment
-
-if __name__ == '__main__':
-    deployment = OpenstackDashboardBasicDeployment(series='artful')
-    deployment.run_tests()
-
-# NOTE(admcleod):  Artful target disabled, pending bug:
-# https://bugs.launchpad.net/charm-percona-cluster/+bug/1728132