Quentin 16/09/2020: TSWATER bugfix: major correction on reading the land mask...

Quentin 16/09/2020: TSWATER bugfix: major correction on reading the land mask for interpolation of inland temperature TSWATER from GRIB file for AROME, ARPEGE, IFS and MOCAGE. The bug is present since MNH541 July 2018 when GFS was introduced. For all models, the land mask is 1=land ; 0=sea/inland water. Then, the surface temperature of the lakes is XUNDEF for PMASK/=0. With PMASK/=1 the surface temperature of the lakes was equal to land surface temperature (T2 in the grib)