add _find_caller to the request log

inspect the call stack to find the part of the test class that
called this rest request. This makes it easier to start from
the tempest log and figure out what rest calls were being made
over the various services, and how the succeeded or not.

Change-Id: Icfd08d5b35a4fd3fdde93042e158ee42424899bf
add request timing

Time every request that we make from the base rest client so we
can see the API call time as part of normal tempest runs. This is
much more useful than this being done inside the servers, as this
will account for the entire call time from the outside.

Change-Id: I9c367a8fd05ae7996e5491a525d92c75d0275b2b
Merge "add _find_caller to the request log"
Merge "add request timing"