Avoid processing cmds until time changes as this means out of order track
entries are processed appropriately.
(Normally a 'completed' is immediately followed by a track entry for the original
cmd - but sometimes the track entry comes a bit later after some other
unrelated cmds are logged. Previously this would lead to being treated as extra
cmds and ones which would never be completed. This in turn lead to lots of
performance loss in processCompletedCommands() function)