Raise NotImplementedError in NeutronV2 API

Remove unused code in nova.network.neutronv2 that returns an empty
list. Instead of just returning an empty list, let's be more explicit
and raise a NotImplementedError. This will be more descriptive if
someone is trying to use this part of the NeutronAPI.

Commit 45e92d4703 contains the changes to use the db layer instead of
the network rpcapi.

Change-Id: I2a9ada8186fd4165c7fceb15965055b5793e6e2c
Closes-Bug: 1258380
Add version 2.0 of conductor rpc interface

This commit adds a new major revision to the rpc interface used to
talk to the conductor service.  The old version will be retained in
Icehouse for Havana rolling upgrade capability.  1.x can be dropped
as soon as Juno development opens.

When 1.x gets dropped, we will be able to remove the following methods
from the conductor manager, as well as all other supporting code for
these methods throughout the conductor:

 - ping()
 - instance_get()
 - instance_get_all()
 - migration_get()
 - migration_get_unconfirmed_by_dest_compute()
 - migration_create()
 - migration_update()
 - aggregate_get()
 - aggregate_get_by_host()
 - aggregate_metadata_add()
 - aggregate_metadata_delete()
 - get_backdoor_port()
 - security_group_get_by_instance()
 - security_group_rule_get_by_security_group()
 - block_device_mapping_destroy()
 - instance_get_all_hung_in_rebooting()
 - instance_info_cache_update()
 - instance_type_get()
 - vol_get_usage_by_time()
 - vol_usage_update()
 - compute_stop()
 - compute_confirm_resize()
 - compute_reboot()

We can also drop backwards compatibility handling for the absence of
any parameters added to other methods during 1.x.

Note that the client side will only send 2.0 messages, but that's
fine.  We expect the nova-conductor service to get updated at the same
time as, or before anything that uses this client code.

For more information on this type of change, see:
https://wiki.openstack.org/wiki/RpcMajorVersionUpdates

Part of blueprint rpc-major-version-updates-icehouse

Change-Id: Ic443c02b1342cceb8c86c37b51af03094157bc48
Cells API calls return 501 when cells disabled

When cells is not enabled the cells API calls should return
a 501 NotImplemented rather than have the internals
eventually raise various errors which may include timeout
errors.

+DocImpact: cells API calls will now return a 501 if cells is disabled
Closes-Bug: 1288214

Change-Id: I07e69bbe11ec88cd3f07b47846f3a0a5c9e6f3dc
Merge "Cells API calls return 501 when cells disabled"
Merge "Add version 2.0 of conductor rpc interface"
Merge "Raise NotImplementedError in NeutronV2 API"