init: Add a unit test for the "start console" action

Treehugger starts Cuttlefish with the console disabled. Add a test that
enables the console. The purpose of this test is to trigger the code paths
in Service::Start() that are unique to processes associated with a
console.

Bug: 213617178
Change-Id: I834632ce6ec5c237c9c2c3f5b1aa7bc98c3ef260
Signed-off-by: Bart Van Assche <bvanassche@google.com>