When a request that is being profiled completes and the response is
received, the middleware expires the profiling cookie. It also needs
to delete the profiling object that holds the base_id UUID so a new
base_id will be created for the next profile. Otherwise the same
base_id is used for subsequent queries and they become merged togther
in the database.

Change-Id: I379cebfa2ed5282c96df0e255a8ba04c65a8523c
Closes-Bug: #1777486
Depends-On: https://review.openstack.org/578362