Cold start soil temperature initialization when excess ice is on.

[mvdebolskiy]

          I have added a use_fates that encompasses the code in question as suggested by @wwieder in issue #2373 .  The test now passes. However, a couple of questions.

1. The setting of t_soisno to 5deg below the freezing temperature when excess_ice is on is outside of the use_fates check and so if the test is changed so that excess_ice is on ( the current default is off), this test will fail (confirmed). I'm not sure what the future plans for excess_ice are and if it is intended for use with FATES.
2. There is an indication from the excess_ice PR (Adding excess ground ice to CTSM  #1787) that it might be ok to set the initial soil temperature to 272K instead of tfrz-5. This would simplify the code, particularly if we want to run FATES with excess_ice on. "src/biogeophys/TemperatureType.F90 -- initial soil temperature set to 268.15 K at the cold start (might be redundant if Initialize t_soisno to 272K instead of 274K to avoid deep soil carbon in permafrost regions #1460 is added)"

Originally posted by @olyson in #2355 (comment)

[mvdebolskiy]

Proposed fix:

• Remove condition for use_excess_ice in TemperatureType.F90
• Change soil temperature below 0.5 m to ~272 K in the WaterStateType.F90 InitCold when excess ice is read only for soil columns in grid cells that have excess ice.
• Comment TemperatureType.F90 that soil temperature will get adjusted later.
• Check if FATES vegetation doesn't die in the grid cells with excess ice on in the first few years.
• Check if FatesHydro doesn't fall apart.

Related Issues and PRs: #2373 #2338 #2355

Excess ice can then be turned on as default.

[ekluzek]

@mvdebolskiy will create a PR with these changes and then have @olyson test it.