LArCondUtils: Preparing to make CaloDD immutable.

Previously, we were creating the CaloDD via a converter, then applying alignments via conditions callbacks. This this meant that the CaloDD will be different depending on whether we're looking before or after alignments have been applied. This can then lead to problems if the CaloDD is retrieved too early. The const_cast'ing needed is also problematic for MT.

Instead of building CaloDD via a converter, we want to move to creating it explicitly as part of doing alignments.

However, this means that in general, we shouldn't be trying to retrieve CaloDetDescrManager during initialize(). Rework to avoid this.