Set the missed test group presubmit for mapping validation

Test: unit tests
Bug: 178646865
Change-Id: Ic0cdfccb3edb7c097676ba200d132bc186076bbe
diff --git a/tests/src/com/android/tradefed/presubmit/HostUnitTestsConfigValidation.java b/tests/src/com/android/tradefed/presubmit/HostUnitTestsConfigValidation.java
index eb72e51..ee36a7e 100644
--- a/tests/src/com/android/tradefed/presubmit/HostUnitTestsConfigValidation.java
+++ b/tests/src/com/android/tradefed/presubmit/HostUnitTestsConfigValidation.java
@@ -138,7 +138,10 @@
 
         Set<TestInfo> testInfosToRun =
                 TestMapping.getTests(
-                        mBuild, /* group */ null, /* host */ true, /* keywords */ new HashSet<>());
+                        mBuild, /* group */
+                        "presubmit", /* host */
+                        true, /* keywords */
+                        new HashSet<>());
 
         List<String> errors = new ArrayList<>();
         List<String> configs = new ArrayList<>();