Update RUC LSM to the latest version used in version 1 of RRFS. (#2028)

TYPE: bug fix, enhancement

KEYWORDS: snow model, irrigation, conductivities

SOURCE: Tanya Smirnova, NOAA/GSL

DESCRIPTION OF CHANGES:

1. Changes to the snow model. Added options to compute thermal snow conductivity and snow cover fraction:
isncond_opt = 1 or 2 (1 is default, 2 is recommended to use) isncov_opt = 1, 2 or 3 (1 is default, 2 is recommended to use for more accurate SCF)
2. Changes to irrigation scheme, use real-time vegetation fraction as an indicator of crops maturity.
3. Changes to soil diffusional and hydraulic conductivities.

LIST OF MODIFIED FILES:
M phys/module_sf_ruclsm.F

TESTS CONDUCTED:
- Tested in RRFS
- The Jenkins tests are all passing.

RELEASE NOTE: This PR modifies the RUC LSM to add options to the snow model, use real-time vegetation fraction as an indicator for irrigation scheme, and change soil diffusional and hydraulic conductivities.