TEST_HEAD test case input files need to be changed from MUD to SAND

[rsignell]

The code is okay, but I needed to make some modifications to the supplied TEST_HEAD input files to get bedload to be non-zero. These modifications are required because of the change in R224, where bedload was split from the other routines, and the looping was changed to DO ised=NCS+1,NST, yet the input files still used NCS=1, NNT=0 (NST=1), so the loop never gets executed.

I needed to modify the ocean_test_head.in file to set NCS=0, NNS=1, modify the sediment_test_head.in file to specify parameters for SAND instead of MUD, and also change the variable names from MUDFRAC_01 to SANDFRAC_01, MUD_01 to SAND_01, etc in the initialization NetCDF file test_head_ini.nc. Once I made these changes, the TEST_HEAD test case run with the R271 code (current trunk code) produced non-zero bedload values equivalent to versions prior to R224.

[arango]

Yes, thank you.