test: negate scale_factor and add_offset of y(y)

PUG expectation is that positive y angles are north of equator
If this is not correct for Japan sector, look at reversing y array instead of negating sf/ao

py/hsd2nc.py

@@ -264,8 +264,9 @@ class NetCDF4_writer(object):
     def set_fgf(self, fgf, downsample_factor=1):
         if self.fgf_y is not None:
             self.fgf_y[:] = fgf.y
-            self.fgf_y.scale_factor = fgf.my * float(downsample_factor)
-            self.fgf_y.add_offset = fgf.by
+            LOG.warning('negating y scale/offset to conform to northward-positive PUG expectation')
+            self.fgf_y.scale_factor = -fgf.my * float(downsample_factor)
+            self.fgf_y.add_offset = -fgf.by
         if self.fgf_x is not None:
             self.fgf_x[:] = fgf.x
             self.fgf_x.scale_factor = fgf.mx * float(downsample_factor)