tests are 'leaking files'

[duncan]

It would be great if, when executing inundation\test_all, it didn't create files in the inundation directory. Currently it does, since some tests create files and then don't delete these files.

Here's a list of files it creates;

bedslope.sww datatest_elevation datatest_elevation.ers most_small_ua.nc most_small_va.nc most_small_ha.nc most_small_e.nc test_windstress_from_file.tms test_windstress_from_file.txt