Introduce the Service::CheckConsole() method

The Service::Start() method is so long that its length negatively
affects readability of the code. Hence this patch that splits
Service::Start().

Test: Booted Android in Cuttlefish.
Change-Id: Ib8e1e87fbd335520cbe3aac2a88d250fcf3b4ff0
Signed-off-by: Bart Van Assche <bvanassche@google.com>