* Modify iteration loop to finish at maxRunTime
* Modify iteration loop to finish at maxRunTime

  Normally the iteration loop runs for FORCING_DURATION seconds.  However, if
  the current time exceeds the max run time, the loop should exit.  This now
  happens.  In previous sbm versions the max run time had to be a multiple
  of FORCING_DURATION, which is why this wasn't a problem before.
csdms-contrib/sbm