Add MicrodroidHostTestCases to TEST_MAPPING

Microdroid shares adbd APEX with its host. This change adds
MicrodroidHostTestCases to TEST_MAPPING to ensure that Microdroid tests
can verify patches to adbd APEX.

Test: presubmit
Change-Id: Iadddae0632dbca7f1613be91843ca76920edb11f
diff --git a/TEST_MAPPING b/TEST_MAPPING
index 238fb54..8733d77 100644
--- a/TEST_MAPPING
+++ b/TEST_MAPPING
@@ -19,6 +19,9 @@
     },
     {
       "name": "adb_tls_connection_test"
+    },
+    {
+      "name": "MicrodroidHostTestCases"
     }
   ],
   "imports": [