test: Make surface demos reproducible by setting colormap to default at start of demo. * bicubic.m, interp2.m, interpn.m, griddata.m, image.m, axis.m, clabel.m, colorbar.m, contour.m, contourf.m, cylinder.m, ezcontour.m, ezcontourf.m, ezmesh.m, ezmeshc.m, ezsurf.m, ezsurfc.m, hold.m, pcolor.m, plotyy.m, quiver3.m, ribbon.m, shading.m, slice.m, sombrero.m, surf.m, surfc.m, surfnorm.m, trisurf.m: Set colormap to default at start of demos to make them reproducible.

--- a/scripts/plot/surfnorm.m
+++ b/scripts/plot/surfnorm.m
@@ -144,16 +144,18 @@
 
 %!demo
 %! clf;
-%! colormap (jet (64));
+%! colormap ('default');
 %! [x, y, z] = peaks (10);
 %! surfnorm (x, y, z);
 
 %!demo
 %! clf;
+%! colormap ('default');
 %! surfnorm (peaks (10));
 
 %!demo
 %! clf;
+%! colormap ('default');
 %! surfnorm (peaks (32));
 %! shading interp;