Move manager options into nova.service

Move the compute_manager, console_manager, cert_manager, network_manager
and scheduler_manager options into nova.service.

Apart from the tests, these options are mostly just used in nova.service
so it makes sense for them to live there. Also, metadata_manager already
lives there.

blueprint: scope-config-opts
Change-Id: I180859817b57c081b83d6a6f075a6ff76bb0ef6d