Move consoleauth_manager option into nova.service and fix imports

Moves the consoleauth_manager option into nova.service like the other
manager options in commit 39ce4032.

The thinking for having it in nova.service is that's where
CONF.get('%_manager'...) is called.  It also makes no sense for the
option to be declared in nova.consoleauth.manager because if you change
this config option, then you don't want nova.consoleauth.manager loaded.

Closes-Bug: #1276398

Change-Id: I85e089239228920e9e58284cf6ff52e43bf85ab0
Merge "Move consoleauth_manager option into nova.service and fix imports"