There used to be 3 states for the SessionManager:
1) Uninitialized (after ctor)
2) A default virgin session
3) Using a session (including the default session)

And we used to switch from state 1 to 2 or 3 after ICore::coreOpened().
This changes that we start in state 2 and thus don't emit a few signals
after coreOpened. I don't think that'll break anything.

Change-Id: I4cf7dade132c9d0ebd6d472d79c8b70c07acd20f
Reviewed-by: Tobias Hunger <tobias.hunger@nokia.com>