Support for etcd on Xenial

Generate etcd config in form suitable for systemd init as well as for
upstart.

Change-Id: I78091d630e95d94e9b6effb077cce1fe63687474

hooks/neutron_api_hooks.py

@@ -652,6 +652,8 @@ def etcd_proxy_force_restart(relation_id=None):
     # treat etcd like the special snowflake it insists on being.
     CONFIGS.register('/etc/init/etcd.conf', [EtcdContext()])
     CONFIGS.write('/etc/init/etcd.conf')
+    CONFIGS.register('/etc/default/etcd', [EtcdContext()])
+    CONFIGS.write('/etc/default/etcd')
 
     if 'etcd-proxy' in CONFIGS.complete_contexts():
         force_etcd_restart()

templates/etcd

@@ -0,0 +1,3 @@
+ETCD_PROXY=on
+ETCD_INITIAL_CLUSTER={{ cluster }}
+ETCD_DATA_DIR=/var/lib/etcd

templates/icehouse/etcd.conf

@@ -9,8 +9,8 @@ respawn
 
 setuid etcd
 
-env ETCD_DATA_DIR=/var/lib/etcd
-export ETCD_DATA_DIR
-
-exec /usr/bin/etcd -proxy on                                                  \
-                   -initial-cluster {{ cluster }}
+script
+  set -a
+  . /etc/default/etcd
+  exec /usr/bin/etcd
+end script

unit_tests/test_neutron_api_hooks.py

@@ -945,4 +945,5 @@ class NeutronAPIHooksTests(CharmTestCase):
     def test_etcd_peer_joined(self):
         self._call_hook('etcd-proxy-relation-joined')
         self.assertTrue(self.CONFIGS.register.called)
-        self.CONFIGS.write.assert_called_with('/etc/init/etcd.conf')
+        self.CONFIGS.write.assert_any_call('/etc/init/etcd.conf')
+        self.CONFIGS.write.assert_any_call('/etc/default/etcd')