Promote HWASan tests to presubmit.

They have been passing and do not show significant slowdown.

Change-Id: I7e0a01b7552f20ce2c5871ad306ca18b1a3f679a
diff --git a/TEST_MAPPING b/TEST_MAPPING
index 570788d..999cb5c 100644
--- a/TEST_MAPPING
+++ b/TEST_MAPPING
@@ -4,7 +4,7 @@
       "name": "bsdiff_unittest"
     }
   ],
-  "hwasan-postsubmit": [
+  "hwasan-presubmit": [
     {
       "name": "bsdiff_unittest"
     }