Fix for-loop type in dumpDispatchStateLocked

Technically the iterator provides a std::pair<const KEY, VALUE>&, so
we're constructing a std::pair<KEY, VALUE> from it and then taking a
const reference to that. This creates an unnecessary copy but then
obscures that by taking a reference to it. We could use the correct type
to avoid this, but a structured binding is even nicer.

Test: compile
Change-Id: I360c4318001eff503b539693166386160bd605eb