Move network_topic into nova.network.rpcapi

The network_topic opt is only used in nova.network.rpcapi and it makes
sense for the RPC module to "own" the topic option.

blueprint: scope-config-opts
Change-Id: Icd779f34df47ac6dd048b3e41995e872d8859872
Move console_topic into nova.console.rpcapi

Even though the console_topic opt is used outside nova.console.rpcapi,
it makes sense for the RPC module to "own" the topic option.

blueprint: scope-config-opts
Change-Id: I0f00927ca1c0bba7b21315240165e83e7075ebb7
Merge "Move network_topic into nova.network.rpcapi"
Merge "Move console_topic into nova.console.rpcapi"