install-guide: systemd reload
install-guide: systemd reload

When adding or changing systemd service files, those files need to be
reloaded. This change adds instructions to the guide for the etcd
service.

Change-Id: I0533aa463506b1b1bdcd0d4849b667c27d35ec60

openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals