Add FHZERO test in OpnReqTest

[junwang-noaa]

Description

It is suggested to add an FHZERO test in the operational requirement test. In this test, when the FHZERO is changed, the forecast output files at certain time and the restart files will not change.

Solution

Based on the control test, we can change FHZERO to a different time, then compare restart files and certain forecast files. For example, change FHZERO from current 6 hours to 3 hours, then the results from fh00-fh03, fh07-fh09, fh13-15, and fh19-21 should be the same in the two runs, while the fh04-fh06, fh10-fh12, fh16-18, will be different due the the different accumulation buckets. So the ORT fhzero test (FHZERO=3) should have the same results at fh21 when compared with the control test (FHZERO=6), and the restart files should also be identical.