testing: reduce sampling on volume tests to make them faster

Signed-off-by: Larry Gritz <lg@larrygritz.com>

Author: lgritz

testsuite/render-mx-anisotropic-vdf/ref/out-linux-alt.exr

@@ -6,5 +6,7 @@
 
 failthresh = 0.01
 failpercent = 1
+allowfailures = 5
+
 outputs = [ "out.exr" ]
-command = testrender("-v -r 196 196 -aa 64 scene.xml out.exr")
+command = testrender("-v -r 196 196 -aa 32 scene.xml out.exr")

testsuite/render-mx-anisotropic-vdf/ref/out-macos-alt.exr

@@ -6,5 +6,7 @@
 
 failthresh = 0.01
 failpercent = 1
+allowfailures = 5
+
 outputs = [ "out.exr" ]
-command = testrender("-r 196 196 -aa 32 scene.xml out.exr")
+command = testrender("-r 196 196 -aa 16 scene.xml out.exr")