This commit removes the following Mitaka deprecated items from the nova
template (and their variable definitions, if any):
- the managers ```compute_manager``` and
```conductor.manager```
- ```security_group_api``` now that it's discovered with
```use_neutron```
- live/block_migration_flag config options
(see also https://review.openstack.org/#/c/263436/)
- ```memcached_servers``` from [DEFAULT] (moved to [cache])
Change-Id: I13c503a0ab23c72f90462cbada50424edbaa71b8
451cd166ce