Lake snow thermal conductivity hard coded to Jordan

[wwieder]

@billsacks noticed this in #3071

It appears in two places for lakes:

CTSM/src/biogeophys/LakeFluxesMod.F90

Line 483 in be65fad

tksur(c) = tkair + (7.75e-5_r8 *bw + 1.105e-6_r8*bw*bw)*(tkice-tkair)

CTSM/src/biogeophys/LakeTemperatureMod.F90

Line 1184 in be65fad

thk(c,j) = tkair + (7.75e-5_r8 *bw + 1.105e-6_r8*bw*bw)*(tkice-tkair)

(Since I saw that the SoilTemperature code was run over non-lake points, I was curious what happened over lakes, so searched for some of the relevant constants in order to find this code.)

Originally posted by @billsacks in #3071