Add a reboot overcloud node method to tripleo topology

So far Tripleo topology module had only methods to power on & off.

After a compute node is turned on, some of the servers/VMs that
are hosted on it can be found on "SHUTOFF" after hypervisor service
is started.

This patch adds the possibility to reboot the TripleO compute node and
making sure all servers which were hosted by this node/hypervisor
will be re-started in case its status doesn't match original status.

Change-Id: I4e15a0d4d739fac37aef150cc18d9dfd9251c37b

tobiko/tripleo/_topology.py

@@ -139,6 +139,43 @@ class TripleoTopologyNode(topology.OpenStackTopologyNode):
 
     overcloud_server: typing.Optional[nova.NovaServer] = None
 
+    def reboot_overcloud_node(self, reactivate_servers=True):
+        """Reboot overcloud node
+
+        This method reboots an overcloud node and may start every server which
+        changed its provisioning state to SHUTOFF because of that operation.
+
+        :param start_servers (bool): whether or not to start the servers which
+            are hosted on the node after the reboot
+        """
+
+        if reactivate_servers:
+            servers_to_restart = self.get_running_servers()
+
+        self.power_off_overcloud_node()
+        self.power_on_overcloud_node()
+
+        if reactivate_servers:
+            for server in servers_to_restart:
+                LOG.debug(f'Server {server.name} with ID {server.id} '
+                          f'had a SHUTOFF status before being '
+                          f'restarted')
+                nova.activate_server(server)
+                LOG.debug(f'Server {server.name} with ID {server.id} '
+                          f'has a {server.status} status after being '
+                          f'restarted')
+
+    def get_running_servers(self):
+        servers_to_reactivate = list()
+        for server in nova.list_servers():
+            server_hyp = getattr(server,
+                                 'OS-EXT-SRV-ATTR:'
+                                 'hypervisor_hostname').split('.', 1)[0]
+            if self.name == server_hyp and server.status != 'SHUTOFF':
+                servers_to_reactivate.append(server)
+        LOG.info(f'Servers to restart after reboot: {servers_to_reactivate}')
+        return servers_to_reactivate
+
     def power_on_overcloud_node(self):
         server = self.overcloud_server
         if server is None: