Reset os_release cache during upgrade

Ensure that the os_release cache is cleared during the openstack
upgrade process, ensuring that package list and configuration
options are correctly set for the new OpenStack version.

Change-Id: Ie685854952527f59ee344bfda8e49250c248150a
Closes-Bug: 1715624

lib/ceilometer_utils.py

@@ -43,6 +43,7 @@ from charmhelpers.contrib.openstack.utils import (
     token_cache_pkgs,
     enable_memcache,
     CompareOpenStackReleases,
+    reset_os_release,
 )
 from charmhelpers.core.hookenv import config, log, is_leader
 from charmhelpers.fetch import apt_update, apt_install, apt_upgrade
@@ -285,6 +286,7 @@ def do_openstack_upgrade(configs):
     ]
     apt_update(fatal=True)
     apt_upgrade(options=dpkg_opts, fatal=True, dist=True)
+    reset_os_release()
     apt_install(packages=get_packages(),
                 options=dpkg_opts,
                 fatal=True)

unit_tests/test_ceilometer_utils.py

@@ -38,6 +38,7 @@ TO_PATCH = [
     'token_cache_pkgs',
     'os_release',
     'is_leader',
+    'reset_os_release',
 ]
 
 
@@ -183,6 +184,7 @@ class CeilometerUtilsTest(CharmTestCase):
         self.configure_installation_source.assert_called_with(
             'cloud:trusty-kilo'
         )
+        self.reset_os_release.assert_called()
 
     def test_get_packages_icehouse(self):
         self.get_os_codename_install_source.return_value = 'icehouse'