Trace exporter should pull osquery details from cached enrollment details instead of querying

[RebeccaMahany]

Once #1986 is complete, we can update the trace exporter to remove osqueryClient entirely. Instead, addAttributesFromOsquery can wait for the enrollment details to be available via the knapsack.

We should check to see if the enrollment details are immediately available (i.e. they've already been cached), and if so, set them at the same time as we set addDeviceIdentifyingAttributes, to avoid having to re-create the exporter unnecessarily.