file frequency for med_phases_history_write is not correct inside fast coupling loop

[DeniseWorthen]

Using med_phases_history_write in the fast coupling loop to write all inst fields in a single file does not create the correct time increment files.

For the following run sequence

runSeq::
@2400
   MED med_phases_prep_ocn_avg
   MED -> OCN :remapMethod=redist
   OCN
   @600
     MED med_phases_prep_atm
     MED med_phases_prep_ice
     MED -> ATM :remapMethod=redist
     MED -> ICE :remapMethod=redist
     ATM
     ICE
     ATM -> MED :remapMethod=redist
     MED med_phases_post_atm
     ICE -> MED :remapMethod=redist
     MED med_phases_post_ice
     MED med_phases_prep_ocn_accum
     MED med_phases_history_write
   @
   OCN -> MED :remapMethod=redist
   MED med_phases_post_ocn
@
::

mediator history files are written correctly until the point when the next file would increment past the slow couple time (in this case, 2400s). For example, the next file in the sequence

ufs.cpld.cpl.hi.2021-03-22-24000.nc
ufs.cpld.cpl.hi.2021-03-22-24600.nc

should be at 25200 seconds (+600s), but the file created is at 27000 secs (+2400s ). Subsequent files are then created at the slow couple loop frequency.

If med_phases_history_write in placed in the slow loop in the above run sequence, all files are created at the right increments.