set_session_extents had a bug; it wasn't calling locations->add()
on the newly created location.
The correct implementation was in set_session_range_location,
but this was only called from one place.
This function was removed, and set_session_extents will be used in its place.
set_session_extents will create a session location if one no longer exists,
so there is no need for set_session_range_location.
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