No other parts of the progress rendering modify the inputs, so we should
avoid this as well.
This actually fixes an edge case in pushWithMoby which writes the same
VertexStatus multiple times, modifying the timestamps and similar.
However, if the operation takes long enough the small time difference
can accumulate, and move the Start time far into the past.
Signed-off-by: Justin Chadwell <me@jedevc.com>