standardize post-call treatment of get_dst_info, delay sorting calls
@jreback we discussed how there are a bunch of functions that do really similar things with `get_dst_info` but have their slight idiosyncrasies.  This standardizes them, and is really verbose so as to delay certain calls until absolutely necessary.

After this we can see about de-duplicating the 6ish occurrences of really similar code by passing a function pointer or something.