CameraITS: relax several test threshold

test_linearity: allow an average error of 2/255.
test_ae_precapture_trigger: allow up to 24 frames.
Also remove test_black_white and test_locked_burst from not yet
mandated list since known issues are resolved.

Bug: 18644101
Change-Id: Id85be9f00f4e2e9118ef9553b50a86b772ae54cb
diff --git a/apps/CameraITS/tests/scene1/test_linearity.py b/apps/CameraITS/tests/scene1/test_linearity.py
index a9063a9..2176f5e 100644
--- a/apps/CameraITS/tests/scene1/test_linearity.py
+++ b/apps/CameraITS/tests/scene1/test_linearity.py
@@ -33,7 +33,7 @@
     """
     NAME = os.path.basename(__file__).split(".")[0]
 
-    RESIDUAL_THRESHOLD = 0.00005
+    RESIDUAL_THRESHOLD = 0.0003 # approximately each sample is off by 2/255
 
     # The HAL3.2 spec requires that curves up to 64 control points in length
     # must be supported.