Change _get_implementation()'s not to do initialization directly.

Many of the initalizations (in eg. framework) have to be done on an
acquire()'d object, so instead of doing the initialization directly, return
the initialization member function back to the createInstance() /
createInstanceWithContext() / ... and perform the initialization there.

As a sideeffect, I belive the calling initialize() from servicemanager is not
that much a hack any more - whoever converts the implementation to be
constructor-base has the choice to provide the callback, or still initialize
through XInitialization, where the callback is preferred by servicemanager
when it exists.

Change-Id: I8a87b75c54c1441ca0f184967d31ff4902fc4081