Fix T78777: Cycles motion blur test differences between AVX/AVX2

This appears to be slight precision differences in the Embree implementation,
simply increase the diff threshold a little for these motion blur tests.

tests/python/modules/render_report.py

@@ -104,6 +104,8 @@ class Report:
         'reference_dir',
         'idiff',
         'pixelated',
+        'fail_threshold',
+        'fail_percent',
         'verbose',
         'update',
         'failed_tests',
@@ -118,6 +120,8 @@ class Report:
         self.reference_dir = 'reference_renders'
         self.idiff = idiff
         self.compare_engines = None
+        self.fail_threshold = 0.016
+        self.fail_percent = 1
 
         self.pixelated = False
         self.verbose = os.environ.get("BLENDER_VERBOSE") is not None
@@ -136,6 +140,9 @@ class Report:
     def set_pixelated(self, pixelated):
         self.pixelated = pixelated
 
+    def set_fail_threshold(self, threshold):
+        self.fail_threshold = threshold
+
     def set_reference_dir(self, reference_dir):
         self.reference_dir = reference_dir
 
@@ -366,8 +373,8 @@ class Report:
             # Diff images test with threshold.
             command = (
                 self.idiff,
-                "-fail", "0.016",
-                "-failpercent", "1",
+                "-fail", str(self.fail_threshold),
+                "-failpercent", str(self.fail_percent),
                 ref_img,
                 tmp_filepath,
             )